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A birth defect, also known as a congenital disorder, is a condition present at
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fe ...

birth
regardless of its cause. Birth defects may result in
disabilities A disability is any condition that makes it more difficult for a person to do certain activities or effectively interact with the world around them (socially or materially). These conditions, or impairments, may be cognitive Cognition () ...

disabilities
that may be
physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor *Physical (album), ''Physical'' (album), a 1981 album by Olivia Newton-John **Physical (Olivia Newton-John song), "Physical" (Olivia Newton-John song) *Physical ( ...
,
intellectual An intellectual is a person who engages in critical thinking Critical thinking is the analysis of facts to form a judgment. The subject is complex; several different Critical thinking#Definitions, definitions exist, which generally includ ...
, or
developmental Development of the human body is the process of growth to maturity. The process begins with fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the ...
. The disabilities can range from mild to severe. Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and
functional disorder A functional disorder is a medical condition that impairs normal functioning of bodily processes that remains largely undetected under examination, dissection or even under a microscope. At the exterior, there is no appearance of abnormality. Thi ...
s in which problems exist with how a body part works. Functional disorders include
metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signaling, signaling and self-sustaining ...
and degenerative disorders. Some birth defects include both structural and functional disorders. Birth defects may result from genetic or chromosomal disorders, exposure to certain medications or chemicals, or certain infections during pregnancy. Risk factors include
folate deficiency Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dieta ...
,
drinking alcohol Alcohol, sometimes referred to by the chemical name ''ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic chemical compound. It is a simple alcohol File:Alcohol general.svg, ...
or
smoking Smoking is a practice in which a substance is burned and the resulting smoke Smoke is a collection of airborne and es emitted when a material undergoes or , together with the quantity of air that is or otherwise mixed into the ma ...

smoking
during pregnancy, poorly controlled
diabetes Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients such as proteins, fats, and carbohydrate ...
, and a mother over the age of 35 years old. Many are believed to involve multiple factors. Birth defects may be visible at birth or diagnosed by screening tests. A number of defects can be detected before birth by different prenatal tests. Treatment varies depending on the defect in question. This may include
therapy A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health Health, according to the , is "a state of complete physical, and social and not merely the absence of and ".. (2006)''Constitution ...
, medication, surgery, or
assistive technology Hearing aid Assistive technology (AT) is assistive, adaptive, and rehabilitative devices for People with disability or the elderly population. People with disability often have difficulty performing activities of daily living Activities of da ...
. Birth defects affected about 96 million people as of 2015. In the United States, they occur in about 3% of newborns. They resulted in about 628,000 deaths in 2015, down from 751,000 in 1990. The types with the greatest numbers of deaths are
congenital heart disease A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps b ...
(303,000), followed by
neural tube defects Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. ...
(65,000).


Classification

Much of the language used for describing congenital conditions antedates
genome mapping Gene mapping describes the methods used to identify the locus of a gene and the distances between genes. Gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Me ...
, and structural conditions are often considered separately from other congenital conditions. Many metabolic conditions are now known to have subtle structural expression, and structural conditions often have genetic links. Still, congenital conditions are often classified in a structural basis, organized when possible by primary organ system affected.


Primarily structural

Several terms are used to describe congenital abnormalities. (Some of these are also used to describe noncongenital conditions, and more than one term may apply in an individual condition.)


Terminology

* A congenital physical anomaly is an abnormality of the structure of a body part. It may or may not be perceived as a problem condition. Many, if not most, people have one or more minor physical anomalies if examined carefully. Examples of minor anomalies can include curvature of the fifth finger (
clinodactyly Clinodactyly is a medical term describing the curvature of a digit (a finger or toe) in the plane of the palm, most commonly the fifth finger (the " pinkie finger") towards the adjacent fourth finger (the "ring finger"). It is a fairly common iso ...

clinodactyly
), a third nipple, tiny indentations of the skin near the ears (preauricular pits), shortness of the fourth
metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the located between the of the fingers and the of the , which forms the connection to the . The metacarpal bones are analogous to the in the foot. Structure T ...
or
metatarsal The metatarsal bones, or metatarsus are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...
bones, or dimples over the lower spine (
sacral dimple A sacral dimple (also termed pilonidal dimple or spinal dimple) is a small depression in the skin, located just above the buttocks The buttocks (singular: buttock) are two rounded portions of the exterior anatomy of most mammals, located on ...
s). Some minor anomalies may be clues to more significant internal abnormalities. * Birth defect is a widely used term for a congenital malformation, ''i.e.'' a congenital, physical anomaly that is recognizable at
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fe ...

birth
, and which is significant enough to be considered a problem. According to the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services The United States Department of Heal ...
(CDC), most birth defects are believed to be caused by a complex mix of factors including genetics, environment, and behaviors,Birth Defects Research
. Centers for Disease Control and Prevention.
though many birth defects have no known cause. An example of a birth defect is
cleft palate A cleft lip contains an opening in the upper lip Lips are a visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Hu ...

cleft palate
, which occurs during the fourth through seventh weeks of gestation. Body tissue and special cells from each side of the head grow toward the center of the face. They join together to make the face. A cleft means a split or separation; the "roof" of the mouth is called the palate. * A congenital malformation is a physical anomaly that is deleterious, ''i.e.'' a structural defect perceived as a problem. A typical combination of malformations affecting more than one body part is referred to as a malformation syndrome. * Some conditions are due to abnormal tissue development: ** A malformation is associated with a disorder of tissue development. Malformations often occur in the first trimester. ** A
dysplasia Dysplasia is any of various types of abnormal growth or development of cells (microscopic scale) or organs (macroscopic scale), and the abnormal histology or anatomical structure resulting from such growth. Dysplasias on a mainly microscopic sca ...
is a disorder at the organ level that is due to problems with tissue development. * Conditions also can arise after tissue is formed: ** A
deformation Deformation can refer to: * Deformation (engineering), changes in an object's shape or form due to the application of a force or forces. ** Deformation (mechanics), such changes considered and analyzed as displacements of continuum bodies. * Defo ...
is a condition arising from mechanical stress to normal tissue. Deformations often occur in the second or third trimester, and can be due to
oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AF ...
. ** A disruption involves breakdown of normal tissues. * When multiple effects occur in a specified order, they are known as a
sequence In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and t ...
. When the order is not known, it is a
syndrome A syndrome is a set of medical signs and symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, rais ...
.


Examples of primarily structural congenital disorders

A limb anomaly is called a
dysmelia Piglet with dipygus at Ukrainian National Chernobyl Museum in Kiev">Ukrainian_National_Chernobyl_Museum.html" ;"title="dipygus at Ukrainian National Chernobyl Museum">dipygus at Ukrainian National Chernobyl Museum in Kiev Dysmelia (from Ancient G ...
. These include all forms of limbs anomalies, such as amelia,
ectrodactyly Ectrodactyly, split hand, or cleft hand (derived from the Greek ''ektroma'' "abortion" and ''daktylos'' "finger") involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malfo ...
,
phocomelia Phocomelia is a condition that involves malformations of human arms and legs. Although many factors can cause phocomelia, the prominent roots come from the use of the drug thalidomide Thalidomide, sold under the brand names Contergan and Thalom ...
,
polymelia Polymelia is a birth defect A birth defect, also known as a congenital disorder, is a condition present at childbirth, birth regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical ...
,
polydactyly Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary body part, supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly (fewer fingers or toes). Signs ...

polydactyly
,
syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), ...

syndactyly
, polysyndactyly,
oligodactyly Oligodactyly (from the Ancient Greek ''oligos'' meaning "few" and δάκτυλος ''daktylos'' meaning "finger") is the presence of fewer than five fingers or toes on a hand or foot.
,
brachydactyly Brachydactyly (Greek language, Greek βραχύς = "short" plus δάκτυλος = "finger"), is a medical term which literally means "short finger" (fingers). The shortness is relative to the length of other long bones and other parts of the bo ...

brachydactyly
,
achondroplasia Achondroplasia is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics, a genome is all genetic information of an organism. It ...
, congenital
aplasia Aplasia (; from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million ...
or
hypoplasia Hypoplasia (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: ...
,
amniotic band syndrome Constriction ring syndrome (CRS) is a congenital disorder A birth defect, also known as a congenital disorder, is a condition present at childbirth, birth regardless of its cause. Birth defects may result in disability, disabilities that may be ...
, and
cleidocranial dysostosis Cleidocranial dysostosis (CCD), also called cleidocranial dysplasia, is a birth defect A birth defect, also known as a congenital disorder, is a condition present at childbirth, birth regardless of its cause. Birth defects may result in disabili ...
.
Congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps ...
s include
patent ductus arteriosus ''Patent ductus arteriosus'' (PDA) is a medical condition in which the ''ductus arteriosus The ductus arteriosus, also called the ductus Botalli, named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus c ...

patent ductus arteriosus
,
atrial septal defect Atrial septal defect (ASD) is a congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart The heart is a cardiac muscle, mu ...

atrial septal defect
,
ventricular septal defect A ventricular septal defect (VSD) is a defect in the ventricular septum The interventricular septum (IVS, or ventricular septum, or during development septum inferius) is the stout wall separating the ventricles, the lower chambers of the hear ...

ventricular septal defect
, and
tetralogy of Fallot Tetralogy of Fallot (TOF), formerly known as Steno-Fallot tetralogy, is a congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the hear ...

tetralogy of Fallot
. Congenital anomalies of the nervous system include neural tube defects such as
spina bifida Spina bifida (Latin for "split spine"; SB) is a in which there is incomplete closing of the and the around the during . There are three main types: spina bifida occulta, meningocele and myelomeningocele. Meningocele and myelomeningocele may ...
,
encephalocele Encephalocele is a neural tube defect characterized by sac-like protrusions of the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the ...
, and
anencephaly Anencephaly is the absence of a major portion of the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sens ...

anencephaly
. Other congenital anomalies of the nervous system include the
Arnold–Chiari malformation Chiari malformation (CM) is a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum (the opening at the base of the skull). CMs can cause headaches, difficulty ...
, the
Dandy–Walker malformation Dandy–Walker malformation (DWM), also known as Dandy–Walker syndrome (DWS), is a rare congenital brain malformation in which the part joining the two Cerebellar hemisphere, hemispheres of the cerebellum (the cerebellar vermis) does not fully ...
,
hydrocephalus :''This article concerns the medical condition. For the hydrocephalus creature in American folklore that bares this condition as a part of its legend, see melon heads.'' Hydrocephalus is a condition in which an accumulation of cerebrospinal flu ...

hydrocephalus
,
microencephaly Microcephaly (from New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was or ...
,
megalencephaly Megalencephaly (or macrencephaly; abbreviated MEG) is a growth development disorder in which the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is loc ...
,
lissencephaly Lissencephaly (, meaning "smooth brain") is a set of rare brain disorders where the whole or parts of the surface of the brain appear smooth. It is caused by Neuronal migration disorder, defective neuronal migration during the 12th to 24th weeks ...

lissencephaly
,
polymicrogyria Polymicrogyria (PMG) is a condition that affects the development of the human brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, ...

polymicrogyria
,
holoprosencephaly Holoprosencephaly (HPE) is a cephalic disorder Cephalic disorders (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located i ...

holoprosencephaly
, and
agenesis of the corpus callosum Agenesis of the corpus callosum (ACC) is a rare Rare may refer to: * Rare, a particular Doneness, temperature of meat * Something infrequent or scarce, see Scarcity :* Rare species, a conservation category in biology designating the scarcity of ...
. Congenital anomalies of the
gastrointestinal system The gastrointestinal tract, (GI tract, GIT, digestive tract, digestion tract, alimentary canal) is the tract from the mouth to the anus which includes all the organs of the digestive system in humans and other animal Animals (also c ...

gastrointestinal system
include numerous forms of
stenosis A stenosis (from Ancient Greek στενός, "narrow") is an abnormal narrowing in a blood vessel or other tubular Organ (anatomy), organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture) ...
and
atresiaAtresia is a condition in which an orifice or passage in the body is (usually abnormally) closed or absent. Examples of atresia include: * Aural atresia, a congenital deformity where the ear canal is underdeveloped. * Biliary atresia, a condition i ...

atresia
, and perforation, such as
gastroschisis Gastroschisis is a birth defect in which the baby's intestines extend outside of the abdomen through a hole next to the belly button. The size of the hole is variable, and other organs including the stomach and liver may also occur outside the bab ...
. Congenital anomalies of the kidney and urinary tract include renal parenchyma, kidneys, and urinary collecting system. Defects can be bilateral or unilateral, and different defects often coexist in an individual child.


Primarily metabolic

A congenital metabolic disease is also referred to as an
inborn error of metabolism Inborn errors of metabolism form a large class of genetic disease A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene In biology, a gene (from ''genos' ...
. Most of these are single-gene defects, usually heritable. Many affect the structure of body parts, but some simply affect the function.


Other

Other well-defined genetic conditions may affect the production of hormones, receptors, structural proteins, and ion channels.


Causes


Alcohol exposure

The mother's consumption of alcohol during pregnancy can cause a continuum of various permanent birth defects: craniofacial abnormalities, brain damage, intellectual disability, heart disease, kidney abnormality, skeletal anomalies, ocular abnormalities. The prevalence of children affected is estimated at least 1% in U.S. as well in Canada. Very few studies have investigated the links between paternal alcohol use and offspring health. However, recent animal research has shown a correlation between paternal alcohol exposure and decreased offspring birth weight. Behavioral and cognitive disorders, including difficulties with learning and memory, hyperactivity, and lowered stress tolerance have been linked to paternal alcohol ingestion. The compromised stress management skills of animals whose male parent was exposed to alcohol are similar to the exaggerated responses to stress that children with
fetal alcohol syndrome Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to ...
display because of maternal alcohol use. These birth defects and behavioral disorders were found in cases of both long- and short-term paternal alcohol ingestion. In the same animal study, paternal alcohol exposure was correlated with a significant difference in organ size and the increased risk of the offspring displaying
ventricular septal defect A ventricular septal defect (VSD) is a defect in the ventricular septum The interventricular septum (IVS, or ventricular septum, or during development septum inferius) is the stout wall separating the ventricles, the lower chambers of the hear ...

ventricular septal defect
s at birth.


Toxic substances

Substances whose
toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect on ...

toxicity
can cause congenital disorders are called
teratogens Teratology is the study of abnormalities of physiological development in all organisms including plants during the entire life span. A sub discipline in Medical Genetics Medical genetics is the branch of medicine that involves the diagnosis and ...
, and include certain pharmaceutical and recreational
drugs in pregnancy Drugs and medications should be avoided while pregnant. Women should speak to their doctor or healthcare professional before starting or stopping any medications while pregnant. Tobacco, alcohol, marijuana, and illicit drug use while pregnant may b ...
, as well as many
environmental toxins in pregnancy A biophysical environment is a biotic and abiotic surrounding of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, ...
. A review published in 2010 identified six main teratogenic mechanisms associated with medication use: folate antagonism,
neural crest cell Neural crest cells are a temporary group of cells unique to vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdo ...
disruption,
endocrine disruption 250px, A comparison of the structures of the natural estrogen hormone nonyl-phenols (right), a xenoestrogen endocrine disruptor">nonylphenol.html" ;"title="estradiol (left) and one of the nonylphenol">nonyl-phenols (right), a xenoestrogen endocri ...
,
oxidative stress Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species Reactive oxygen species (ROS) are highly chemicals formed from O2. Examples of ROS include s, , , , and . The reduction of molecular oxygen ...
,
vascular The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an Biological system, organ system that permits blood to circulate and transport nutrien ...
disruption, and specific receptor- or enzyme-mediated teratogenesis. An estimated 10% of all birth defects are caused by prenatal exposure to a teratogenic agent. These exposures include medication or drug exposures, maternal infections and diseases, and environmental and occupational exposures. Paternal smoking has also been linked to an increased risk of birth defects and childhood cancer for the offspring, where the paternal germline undergoes oxidative damage due to cigarette use. Teratogen-caused birth defects are potentially preventable. Nearly 50% of pregnant women have been exposed to at least one medication during gestation. During pregnancy, a woman can also be exposed to teratogens from contaminated clothing or toxins within the seminal fluid of a partner. An additional study found that of 200 individuals referred for genetic counseling for a teratogenic exposure, 52% were exposed to more than one potential teratogen. The
United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...
studied 1,065 chemical and drug substances in their ToxCast program (part of the
CompTox Chemicals Dashboard The CompTox Chemicals Dashboard is a freely accessible online database created and maintained by the United States Environmental Protection Agency, U.S. Environmental Protection Agency (EPA). The database provides access to multiple types of data ...
) using '' in silica'' modeling and a human
pluripotent Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum, ...
stem cell In multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties ...
-based assay to predict
in vivo Studies Study or studies may refer to: General * Education **Higher education * Clinical trial * Experiment * Observational study * Research * Study skills, abilities and approaches applied to learning Other * Study (art), a drawing or series ...
developmental intoxicants based on changes in cellular
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
following chemical exposure. Findings of the study published in 2020 were that 19% of the 1065 chemicals yielded a prediction of
developmental toxicity Developmental toxicity is any structural or functional alteration, reversible or irreversible, which interferes with homeostasis In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
.


Medications and supplements

Probably, the most well-known teratogenic drug is
thalidomide Thalidomide, sold under the brand names Contergan and Thalomid among others, is a medication used to treat a number of cancers (including multiple myeloma), graft-versus-host disease, and a number of skin conditions including complications of l ...

thalidomide
. It was developed near the end of the 1950s by Chemie Grünenthal as a and
antiemetic An antiemetic is a drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and binders. Aspirin is a pharmaceutical drug A medication (also referred to as medicine, pharmaceutic ...
. Because of its ability to prevent nausea, it was prescribed for pregnant women in almost 50 countries worldwide between 1956 and 1962. Until William McBride published the study leading to its withdrawal from the market at 1961, about 8,000 to 10,000 severely malformed children were born. The most typical disorders induced by thalidomide were reductional deformities of the long bones of the extremities.
Phocomelia Phocomelia is a condition that involves malformations of human arms and legs. Although many factors can cause phocomelia, the prominent roots come from the use of the drug thalidomide Thalidomide, sold under the brand names Contergan and Thalom ...
, otherwise a rare deformity, therefore helped to recognise the teratogenic effect of the new drug. Among other malformations caused by thalidomide were those of ears, eyes, brain, kidney, heart, and digestive and respiratory tracts; 40% of the prenatally affected children died soon after birth. As thalidomide is used today as a treatment for
multiple myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast wi ...

multiple myeloma
and
leprosy Leprosy, also known as Hansen's disease (HD), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. ...

leprosy
, several births of affected children were described in spite of the strictly required use of contraception among female patients treated by it.
Vitamin A Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, (also known as retinaldehyde), retinoic acid and several provitamin A carotenoids (most notably Beta-Carotene, beta-carotene). Vitamin A has mul ...

Vitamin A
is the sole vitamin that is embryotoxic even in a therapeutic dose, for example in
multivitamin A multivitamin is a preparation intended to serve as a dietary supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder or liquid. A supplement can provide nut ...
s, because its metabolite,
retinoic acid Retinoic acid (used simplified here for all-''trans''-retinoic acid) is a metabolite In biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science (from the Latin Latin (, or , ) is ...

retinoic acid
, plays an important role as a signal molecule in the development of several tissues and organs. Its natural precursor, β-carotene, is considered safe, whereas the consumption of animal liver can lead to malformation, as the liver stores lipophilic vitamins, including retinol.
Isotretinoin Isotretinoin, also known as 13-''cis''-retinoic acid and sold under the brand name Accutane among others, is a medication primarily used to treat severe acne Acne, also known as acne vulgaris, is a long-term skin condition A skin condi ...

Isotretinoin
(13-cis-retinoic-acid; brand name Roaccutane), vitamin A analog, which is often used to treat severe
acne Acne, also known as acne vulgaris, is a long-term skin condition A skin condition, also known as cutaneous condition, is any medical condition A disease is a particular abnormal condition that negatively affects the structure or ...

acne
, is such a strong teratogen that just a single dose taken by a pregnant woman (even
transdermal Transdermal is a route of administration A route of administration in pharmacology Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artifi ...
ly) may result in serious birth defects. Because of this effect, most countries have systems in place to ensure that it is not given to pregnant women, and that the patient is aware of how important it is to prevent pregnancy during and at least one month after treatment. Medical guidelines also suggest that pregnant women should limit vitamin A intake to about 700 μg/day, as it has teratogenic potential when consumed in excess. Vitamin A and similar substances can induce spontaneous abortions, premature births, defects of eyes (
microphthalmia Microphthalmia (Greek: μικρός ''mikros'' = small; ὀφθαλμός ''ophthalmos'' = eye), also referred as microphthalmos, is a developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eye ...
), ears, thymus, face deformities, and neurological (
hydrocephalus :''This article concerns the medical condition. For the hydrocephalus creature in American folklore that bares this condition as a part of its legend, see melon heads.'' Hydrocephalus is a condition in which an accumulation of cerebrospinal flu ...

hydrocephalus
, microcephalia) and cardiovascular defects, as well as
mental retardation Intellectual disability (ID), also known as general learning disability and formerly mental retardation (MR),Rosa's Law Rosa's Law is a United States The United States of America (USA), commonly known as the United States (U.S. or US), o ...
.
Tetracycline Tetracycline, sold under the brand name Sumycin among others, is an oral antibiotic An antibiotic is a type of antimicrobial substance active against bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell ...

Tetracycline
, an
antibiotic An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system t ...
, should never be prescribed to women of reproductive age or to children, because of its negative impact on
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
mineralization and teeth mineralization. The "tetracycline teeth" have brown or grey colour as a result of a defective development of both the
dentine Dentin () (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. Curr ...
and the enamel of teeth. Several
anticonvulsants Anticonvulsants (also commonly known as antiepileptic drugs or as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic Epilepsy is a group of neurological disorders characterized by recurrent e ...

anticonvulsants
are known to be highly teratogenic.
Phenytoin Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures (also known as Grand Mal seizures) and focal seizures, but not absence seizures. The intr ...
, also known as diphenylhydantoin, along with
carbamazepine Carbamazepine (CBZ), sold under the trade name Tegretol among others, is an anticonvulsant medication used primarily in the treatment of epilepsy and neuropathic pain. It is used in schizophrenia along with other medications and as a second- ...

carbamazepine
, is responsible for the
fetal hydantoin syndrome Fetal hydantoin syndrome, also called fetal dilantin syndrome, is a group of defects caused to the developing fetus by exposure to teratology, teratogenic effects of phenytoin. Dilantin is the brand name of the drug phenytoin sodium in the United S ...
, which may typically include broad nose base, cleft lip and/or palate, microcephalia, nails and fingers
hypoplasia Hypoplasia (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: ...
,
intrauterine growth restriction Intrauterine growth restriction (IUGR) refers to poor growth of a fetus while in the mother's womb during pregnancy. The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus. At least ...
, and mental retardation. taken during pregnancy is responsible for the fetal trimethadione syndrome, characterized by craniofacial, cardiovascular, renal, and spine malformations, along with a delay in mental and physical development.
Valproate Valproate (VPA) and its valproic acid, sodium valproate, and valproate semisodium forms are medications primarily used to treat epilepsy Epilepsy is a group of non-communicable neurological disorder A neurological disorder is any disorder ...
has
antifolate Antifolates are a class of antimetabolite medications that antagonise (that is, block) the actions of folic acid (vitamin B9). Folic acid's primary function in the body is as a cofactor to various methyltransferases involved in serine, methionine, ...
effects, leading to
neural tube In the developing chordate A chordate () is an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consum ...

neural tube
closure-related defects such as spina bifida. Lower and
autism Autism is a developmental disorder Developmental disorders comprise a group of psychiatric conditions originating in childhood that involve serious impairment in different areas. There are several ways of using this term. The most narro ...

autism
have recently also been reported as a result of intrauterine valproate exposure.
Hormonal contraception Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original h ...
is considered as harmless for the embryo. Peterka and Novotná do, however, state that synthetic
progestin A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug Uncoated tablets, consist ...
s used to prevent miscarriage in the past frequently caused masculinization of the outer reproductive organs of female newborns due to their
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
ic activity.
Diethylstilbestrol Diethylstilbestrol (DES), also known as stilbestrol or stilboestrol, is a nonsteroidal estrogen medication, which is presently rarely used. In the past, it was widely used for a variety of indications, including pregnancy support for women with a ...

Diethylstilbestrol
is a synthetic
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
used from the 1940s to 1971, when the prenatal exposition has been linked to the clear-cell adenocarcinoma of the vagina. Following studies showed elevated risks for other tumors and congenital malformations of the sex organs for both sexes. All
cytostatics Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents) as part of a standardized chemotherapy regimen. ...

cytostatics
are strong teratogens;
abortion Abortion is the ending of a pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism ...

abortion
is usually recommended when pregnancy is discovered during or before chemotherapy.
Aminopterin Aminopterin (or 4-aminopteroic acid), the 4-amino derivative of folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary suppl ...

Aminopterin
, a cytostatic drug with anti
folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
effect, was used during the 1950s and 1960s to induce
therapeutic abortion Abortion is the ending of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion" and occurs in approximately 30% to 40% of pregnancies. ...
s. In some cases, the abortion did not happen, but the newborns suffered a fetal aminopterin syndrome consisting of growth retardation,
craniosynostosis Craniosynostosis is a condition in which one or more of the fibrous sutures Suture, literally meaning "seam", may refer to: Arts, entertainment, and media * Suture (album), ''Suture'' (album), a 2000 album by American Industrial rock band Cheml ...
, hydrocephalus, facial dismorphities, mental retardation, and/or leg deformities


Toxic substances

Drinking water Drinking water, also known as potable water, is water that is safe to drinking, drink or use for food preparation. The amount of drinking water required to maintain good health varies, and depends on physical activity level, age, health-related ...

Drinking water
is often a medium through which harmful toxins travel. Heavy metals, elements, nitrates, nitrites, and fluoride can be carried through water and cause congenital disorders. Nitrate, which is found mostly in drinking water from ground sources, is a powerful teratogen. A case-control study in rural Australia that was conducted following frequent reports of prenatal mortality and congenital malformations found that those who drank the nitrate-containing groundwater, as opposed to rain water, ran the risk of giving birth to children with central nervous system disorders, muscoskeletal defects, and cardiac defects. Chlorinated and aromatic solvents such as benzene and trichloroethylene sometimes enter the water supply due to oversights in waste disposal. A case-control study on the area found that by 1986, leukemia was occurring in the children of Woburn, Massachusetts, at a rate that was four times the expected rate of incidence. Further investigation revealed a connection between the high occurrence of leukemia and an error in water distribution that delivered water to the town with significant contamination with manufacturing waste containing trichloroethylene. As an
endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine The endocrine system is a messenger system compri ...
,
DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless Crystallinity, crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmen ...

DDT
was shown to induce
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the natural loss of an embryo or fetus before it is fetal viability, able to survive independently. Some use the cutoff of 20 weeks of gestation, after whi ...
s, interfere with the development of the
female reproductive system The female reproductive system is made up of the internal and external sex organs that function in reproduction of new offspring. In humans, the female reproductive system is immature at birth and develops to maturity at puberty to be able to ...

female reproductive system
, cause the
congenital hypothyroidism Congenital hypothyroidism (CH) is thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4. rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-rele ...
, and suspectibly childhood obesity. Fluoride, when transmitted through water at high levels, can also act as a teratogen. Two reports on fluoride exposure from China, which were controlled to account for the education level of parents, found that children born to parents who were exposed to 4.12 ppm fluoride grew to have IQs that were, on average, seven points lower than their counterparts whose parents consumed water that contained 0.91 ppm fluoride. In studies conducted on rats, higher fluoride in drinking water led to increased acetylcholinesterase levels, which can alter prenatal brain development. The most significant effects were noted at a level of 5 ppm. The fetus is even more susceptible to damage from carbon monoxide intake, which can be harmful when inhaled during pregnancy, usually through first- or second-hand tobacco smoke. The concentration of carbon monoxide in the infant born to a nonsmoking mother is around 2%, and this concentration drastically increases to a range of 6%–9% if the mother smokes tobacco. Other possible sources of prenatal carbon monoxide intoxication are exhaust gas from combustion motors, use of dichloromethane (paint thinner, varnish removers) in enclosed areas, defective gas water heaters, indoor barbeques, open flames in poorly ventilated areas, and atmospheric exposure in highly polluted areas. Exposure to carbon monoxide at toxic levels during the first two trimesters of pregnancy can lead to intrauterine growth restriction, leading to a baby who has stunted growth and is born smaller than 90% of other babies at the same gestational age. The effect of chronic exposure to carbon monoxide can depend on the stage of pregnancy in which the mother is exposed. Exposure during the embryonic stage can have neurological consequences, such as telencephalic dysgenesis, behavioral difficulties during infancy, and reduction of cerebellum volume. Also, possible skeletal defects could result from exposure to carbon monoxide during the embryonic stage, such as hand and foot malformations,
hip dysplasia Hip dysplasia is an abnormality of the hip joint In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdo ...
, hip subluxation, agenesis of a limb, and inferior maxillary atresia with
glossoptosisGlossoptosis is a medical condition and abnormality which involves the downward displacement or retraction of the tongue The tongue is a muscular organ in the mouth of a typical vertebrate. It manipulates food for mastication and swallowing ...
. Also, carbon monoxide exposure between days 35 and 40 of embryonic development can lead to an increased risk of the child developing a cleft palate. Exposure to carbon monoxide or polluted ozone exposure can also lead to cardiac defects of the ventrical septal, pulmonary artery, and heart valves. The effects of carbon monoxide exposure are decreased later in fetal development during the fetal stage, but they may still lead to
anoxic The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of disso ...
encephalopathy Encephalopathy (; from grc, ἐνκέφαλος "brain" + πάθος "suffering") means any disorder or disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and orga ...
. Industrial pollution can also lead to. Over a period of 37 years, the Chisso Corporation, a petrochemical and plastics company, contaminated the waters of Minamata Bay with an estimated 27 tons of methylmercury, contaminating the local water supply. This led to many people in the area to develop what became known as the "Minamata disease". Because methylmercury is a teratogen, the mercury poisoning of those residing by the bay resulted in neurological defects in the offspring. Infants exposed to mercury poisoning ''in utero ''showed predispositions to
cerebral palsy Cerebral palsy (CP) is a group of movement disorders Movement disorder refers to any clinical syndrome with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity Spasticity () is ...

cerebral palsy
,
ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality Gait abnormality is a deviation from normal walking ( gait). Watching a patient walk is the most important part ...

ataxia
, inhibited psychomotor development, and mental retardation. Landfill sites have been shown to have adverse effects on fetal development. Extensive research has shown that landfills have several negative effects on babies born to mothers living near landfill sites: low birth weight, birth defects, spontaneous abortion, and fetal and infant mortality. Studies done around the
Love Canal Love Canal is a neighborhood in Niagara Falls, New York Niagara Falls is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The ...
site near Niagara Falls and the Lipari Landfill in New Jersey have shown a higher proportion of low birth-weight babies than communities farther away from landfills. A study done in California showed a positive correlation between time and quantity of dumping and low birth weights and neonatal deaths. A study in the United Kingdom showed a correlation between pregnant women living near landfill sites and an increased risk of congenital disorders, such as neural tube defects,
hypospadias Hypospadias is a common variation in fetal development of the penis in which the urethra does not open from its usual location in the head of the penis. It is the second-most common birth abnormality of the male reproductive system, affecting abo ...

hypospadias
, epispadia, and
abdominal wall defects Abdominal wall defects are a type of congenital defect that allows the stomach, the intestines, or other organs to protrude through an unusual opening that forms on the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) ...
, such as
gastroschisis Gastroschisis is a birth defect in which the baby's intestines extend outside of the abdomen through a hole next to the belly button. The size of the hole is variable, and other organs including the stomach and liver may also occur outside the bab ...
and exomphalos. A study conducted on a Welsh community also showed an increase incidence of gastroschisis. Another study on 21 European hazardous-waste sites showed that those living within 3 km had an increased risk of giving birth to infants with birth defects and that as distance from the land increased, the risk decreased. These birth defects included neural tube defects, malformations of the cardiac septa, anomalies of arteries and veins, and chromosomal anomalies. Looking at communities that live near landfill sites brings up environmental justice. A vast majority of sites are located near poor, mostly black, communities. For example, between the early 1920s and 1978, about 25% of Houston's population was black. However, over 80% of landfills and incinerators during this time were located in these black communities. Another issue regarding
environmental justice Environmental justice is a social movement A social movement is a loosely organized effort by a large group of people to achieve a particular goal, typically a social Social organisms, including humans, live collectively in interacting p ...
is
lead poisoning Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning Metal toxicity or metal poisoning is the toxic effect of certain metals in certain forms and doses on life. Some metals are toxic when they form poisonous solubl ...
. A fetus exposed to lead during the pregnancy can result in learning difficulties and slowed growth. Some paints (before 1978) and pipes contain lead. Therefore, pregnant women who live in homes with lead paint inhale the dust containing lead, leading to lead exposure in the fetus. When lead pipes are used for drinking water and cooking water, this water is ingested, along with the lead, exposing the fetus to this toxin. This issue is more prevalent in poorer communities because more well-off families are able to afford to have their homes repainted and pipes renovated.


Smoking

Paternal smoking prior to conception has been linked with the increased risk of congenital abnormalities in offspring. Smoking causes DNA mutations in the germline of the father, which can be inherited by the offspring. Cigarette smoke acts as a chemical mutagen on germ cell DNA. The germ cells suffer oxidative damage, and the effects can be seen in altered mRNA production, infertility issues, and side effects in the embryonic and fetal stages of development. This
oxidative damage (mild reducing agent) are added to powdered potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4 and composed of potassium ion, K+ and permanganate, . It is a purplish-black crystalline salt, th ...
may result in epigenetic or genetic modifications of the father's germline. Fetal
lymphocytes A lymphocyte is a type of white blood cell in the immune system of gnathostomata, jawed vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated immunity, cell-mediated, cytotoxicity, cytotoxic innate immune system, i ...

lymphocytes
have been damaged as a result of a father's smoking habits prior to conception. Correlations between paternal smoking and the increased risk of offspring developing childhood cancers (including acute
leukemia Leukemia ( also spelled leukaemia and pronounced ), is a group of blood cancer Tumors of the hematopoietic and lymphoid tissues (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English ...

leukemia
,
brain tumors A brain tumor occurs when abnormal cells form within the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on ...
, and
lymphoma Lymphoma is a group of blood cancer, blood malignancies that develop from lymphocytes (a type of white blood cell). The name often refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include Lymphadenopathy, ...

lymphoma
) before age five have been established. Little is currently known about how paternal smoking damages the fetus, and what window of time in which the father smokes is most harmful to offspring.


Infections

A
vertically transmitted infection A vertically transmitted infection is an infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an eve ...
is an
infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

infection
caused by
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
,
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
es, or in rare cases,
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
s transmitted directly from the mother to an
embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...

embryo
,
fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism tha ...

fetus
, or baby during pregnancy or childbirth. Congenital disorders were initially believed to be the result of only hereditary factors. However, in the early 1940s, Australian pediatric ophthalmologist
Norman Gregg Sir Norman McAlister Gregg, (7 March 1892 – 27 July 1966) was an Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian con ...

Norman Gregg
began recognizing a pattern in which the infants arriving at his surgery were developing congenital cataracts at a higher rate than those who developed it from hereditary factors. On October 15, 1941, Gregg delivered a paper that explained his findings-68 out of the 78 children who were afflicted with congenital cataracts had been exposed'' in utero'' to rubella due to an outbreak in Australian army camps. These findings confirmed, to Gregg, that, in fact, environmental causes for congenital disorders could exist.
Rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

Rubella
is known to cause abnormalities of the eye, internal ear, heart, and sometimes the teeth. More specifically, fetal exposure to rubella during weeks five to ten of development (the sixth week particularly) can cause
cataracts A cataract is a cloudy area in the lens A lens is a transmissive optical Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'natur ...

cataracts
and
microphthalmia Microphthalmia (Greek: μικρός ''mikros'' = small; ὀφθαλμός ''ophthalmos'' = eye), also referred as microphthalmos, is a developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eye ...
in the eyes. If the mother is infected with rubella during the ninth week, a crucial week for internal ear development, destruction of the
organ of Corti The organ of Corti, or spiral organ, is the receptor organ for hearing and is located in the mammalian cochlea The cochlea is the part of the inner ear Inner Ear (established in 2007 in Bodø, Norway) is a Norwegian record label initiated an ...

organ of Corti
can occur, causing deafness. In the heart, the
ductus arteriosus The ''ductus arteriosus'', also called the ''ductus Botalli'', named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta. It all ...
can remain after birth, leading to hypertension. Rubella can also lead to atrial and ventricular septal defects in the heart. If exposed to rubella in the second trimester, the fetus can develop central nervous system malformations. However, because infections of rubella may remain undetected, misdiagnosed, or unrecognized in the mother, and/or some abnormalities are not evident until later in the child's life, precise incidence of birth defects due to rubella are not entirely known. The timing of the mother's infection during fetal development determines the risk and type of birth defect. As the embryo develops, the risk of abnormalities decreases. If exposed to the rubella virus during the first four weeks, the risk of malformations is 47%. Exposure during weeks five through eight creates a 22% chance, while weeks 9-12, a 7% chance exists, followed by 6% if the exposure is during the 13th-16th weeks. Exposure during the first eight weeks of development can also lead to premature birth and fetal death. These numbers are calculated from immediate inspection of the infant after birth. Therefore, mental defects are not accounted for in the percentages because they are not evident until later in the child's life. If they were to be included, these numbers would be much higher. Other infectious agents include
cytomegalovirus ''Cytomegalovirus'' (''CMV'') (from ''cyto-'' 'cell' via Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. I ...
, the
herpes simplex virus Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), also known by their taxonomical names ''Human alphaherpesvirus 1'' and ''Human alphaherpesvirus 2'', are two members of the Herpesviridae#Human herpesvirus types, human ''Herpesviridae'' family, a ...
,
hyperthermia Hyperthermia, also known simply as overheating, is a condition where an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat In thermodynamics, heat is ...
,
toxoplasmosis Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis usually cause no obvious symptoms in adults. Occasionally, people may have a few weeks or months of mild, flu-like illness such as ...
, and
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal disease, are infection An infection is the invasion of an orga ...
. Maternal exposure to cytomegalovirus can cause
microcephaly Microcephaly (from New Latin New Latin (also called Neo-Latin or modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally sp ...

microcephaly
, cerebral calcifications, blindness, chorioretinitis (which can cause blindness),
hepatosplenomegaly Hepatosplenomegaly (commonly abbreviated HSM) is the simultaneous enlargement of both the liver The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary f ...
, and meningoencephalitis in fetuses. Microcephaly is a disorder in which the fetus has an atypically small head, cerebral calcifications means certain areas of the brain have atypical calcium deposits, and meningoencephalitis is the enlargement of the brain. All three disorders cause abnormal brain function or mental retardation. Hepatosplenomegaly is the enlargement of the liver and spleen which causes digestive problems. It can also cause some
kernicterus Kernicterus is a bilirubin-induced brain dysfunction. The term was coined in 1904 by Christian Georg Schmorl, Schmorl. Bilirubin is a naturally occurring substance in the body of humans and many other animals, but it is neurotoxicity, neurotoxic ...

kernicterus
and
petechiae A petechia (pl. petechiae) is a small (1–2 mm) red or purple spot on the skin or conjunctiva The conjunctiva is a tissue that lines the inside of the eyelid An eyelid is a thin fold of skin that covers and protects an eye. The leva ...
. Kernicterus causes yellow pigmentation of the skin, brain damage, and deafness. Petechaie is when the capillaries bleed resulting in red/purple spots on the skin. However, cytomegalovirus is often fatal in the embryo. The herpes simplex virus can cause
microcephaly Microcephaly (from New Latin New Latin (also called Neo-Latin or modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally sp ...

microcephaly
, microphthalmus (abnormally small eyeballs), retinal dysplasia,
hepatosplenomegaly Hepatosplenomegaly (commonly abbreviated HSM) is the simultaneous enlargement of both the liver The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary f ...
, and mental retardation. Both microphthalmus and retinal dysplasia can cause blindness. However, the most common symptom in infants is an inflammatory response that develops during the first three weeks of life. Hyperthermia causes
anencephaly Anencephaly is the absence of a major portion of the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sens ...

anencephaly
, which is when part of the brain and skull are absent in the infant. Mother exposure to toxoplasmosis can cause cerebral calcification, hydrocephalus (causes mental disabilities), and mental retardation in infants. Other birth abnormalities have been reported as well, such as chorioretinitis, microphthalmus, and ocular defects. Syphilis causes congenital deafness, mental retardation, and diffuse fibrosis in organs, such as the liver and lungs, if the embryo is exposed.


Lack of nutrients

For example, a lack of
folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins B vitamins are a class of water-soluble vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds ar ...

folic acid
, a B vitamin, in the diet of a mother can cause cellular
neural tube In the developing chordate A chordate () is an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consum ...

neural tube
deformities that result in spina bifida. Congenital disorders such as a neural tube deformity can be prevented by 72% if the mother consumes 4 mg of folic acid before the conception and after 12 weeks of pregnancy. Folic acid, or vitamin B9, aids the development of the foetal nervous system. Studies with mice have found that food deprivation of the male mouse prior to conception leads to the offspring displaying significantly lower blood glucose levels.


Physical restraint

External physical shocks or constraint due to growth in a restricted space may result in unintended deformation or separation of cellular structures resulting in an abnormal final shape or damaged structures unable to function as expected. An example is
Potter syndrome Potter sequence is the atypical physical appearance of a baby due to oligohydramnios Oligohydramnios is a condition in pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring develops inside a woman. A ...
due to
oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AF ...
. This finding is important for future understanding of how genetics may predispose individuals for diseases such as obesity, diabetes, and cancer. For multicellular organisms that develop in a
womb The uterus (from Latin "uterus", plural ''uteri'') or womb () is the main female hormone-responsive, sex organ, secondary sex organ of the reproductive system in humans and most other mammals. Things occurring in the uterus are described with th ...
, the physical interference or presence of other similarly developing organisms such as
twins Twins are two offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a ...

twins
can result in the two cellular masses being integrated into a larger whole, with the combined cells attempting to continue to develop in a manner that satisfies the intended growth patterns of both cell masses. The two cellular masses can compete with each other, and may either duplicate or merge various structures. This results in conditions such as
conjoined twins Conjoined twins – sometimes popularly referred to as Siamese twins – are identical twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygo ...
, and the resulting merged organism may die at birth when it must leave the life-sustaining environment of the womb and must attempt to sustain its biological processes independently.


Genetics

Genetic causes of birth defects include
inheritance Inheritance is the practice of passing on private property Private property is a legal designation for the ownership of property by non-governmental legal entities. Private property is distinguishable from public property Public property i ...

inheritance
of abnormal
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
s from the mother or the father, as well as new
mutation In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
s in one of the
germ cell A germ cell is any biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the smallest units of life, and hence are often referred to a ...
s that gave rise to the fetus. Male germ cells mutate at a much faster rate than female germ cells, and as the father ages, the DNA of the germ cells mutates quickly. If an egg is fertilized with sperm that has damaged DNA, a possibility exists that the fetus could develop abnormally.
Genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and li ...
s are all congenital (present at birth), though they may not be expressed or recognized until later in life. Genetic disorders may be grouped into single-gene defects, multiple-gene disorders, or chromosomal defects. Single-gene defects may arise from abnormalities of both copies of an
autosomal An autosome is any chromosome that is not a sex chromosome (an allosome). The members of an autosome pair in a diploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the ...
gene (a
recessive In genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist ...
disorder) or of only one of the two copies (a
dominant Domination or dominant may refer to: Society * World domination, which is mainly a conspiracy theory * Colonialism in which one group (usually a nation) invades another region for material gain or to eliminate competition * Chauvinism in which a p ...
disorder). Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Large chromosomal abnormalities always produce effects on many different body parts and organ systems.


Socioeconomics

A low
socioeconomic status Socioeconomic status (SES) is an economic and sociological combined total measure of a person's work experience and of an individual's or family's economic access to resources and social position in relation to others. When analyzing a family's ...
in a deprived neighborhood may include exposure to "environmental stressors and risk factors". Socioeconomic inequalities are commonly measured by the Cartairs-Morris score, Index of Multiple Deprivation, Townsend deprivation index, and the Jarman score. The Jarman score, for example, considers "unemployment, overcrowding, single parents, under-fives, elderly living alone, ethnicity, low social class and residential mobility". In Vos’ meta-analysis these indices are used to view the effect of low SES neighborhoods on maternal health. In the meta-analysis, data from individual studies were collected from 1985 up until 2008. Vos concludes that a correlation exists between prenatal adversities and deprived neighborhoods. Other studies have shown that low SES is closely associated with the development of the fetus in utero and growth retardation. Studies also suggest that children born in low SES families are "likely to be born prematurely, at low birth weight, or with asphyxia, a birth defect, a disability, fetal alcohol syndrome, or AIDS". Bradley and Corwyn also suggest that congenital disorders arise from the mother's lack of nutrition, a poor lifestyle, maternal substance abuse and "living in a neighborhood that contains hazards affecting fetal development (toxic waste dumps)". In a meta-analysis that viewed how inequalities influenced maternal health, it was suggested that deprived neighborhoods often promoted behaviors such as smoking, drug and alcohol use. After controlling for socioeconomic factors and ethnicity, several individual studies demonstrated an association with outcomes such as perinatal mortality and preterm birth.


Radiation

For the survivors of the
atomic bombing of Hiroshima The United States detonated two nuclear weapons A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive for ...
and
Nagasaki is the capital and the largest city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. ...
, who are known as the ''
Hibakusha ''Hibakusha'' (; ja, 被爆者 or ; "person affected by a bomb" or "person affected by exposure o radioactivity) is a word of Japanese origin generally designating the people affected by the 1945 atomic bombings of Hiroshima and Nagasaki. De ...

Hibakusha
'', no statistically demonstrable increase of birth defects/congenital malformations was found among their later conceived children, or found in the later conceived children of cancer survivors who had previously received
radiotherapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that h ...
. The surviving women of Hiroshima and Nagasaki who were able to conceive, though exposed to substantial amounts of radiation, later had children with no higher incidence of abnormalities/birth defects than in the Japanese population as a whole. Relatively few studies have researched the effects of paternal radiation exposure on offspring. Following the
Chernobyl Chernobyl (, , russian: Чернобыль), also known as Chornobyl ( uk, Чорнобиль, Chornobyl'; ; ), is a partially abandoned city in the Chernobyl Exclusion Zone, situated in the Ivankiv Raion of northern Kyiv Oblast, Ukraine ...

Chernobyl
disaster, it was assumed in the 1990s that the germ line of irradiated fathers suffered
minisatellite A minisatellite is a tract of repetitive in which certain s (ranging in length from 10–60 ) are typically repeated 5-50 times. Minisatellites occur at more than 1,000 locations in the and they are notable for their high mutation rate and high ...
mutations in the DNA, which was inherited by descendants. More recently, however, the World Health Organization states, "children conceived before or after their father's exposure showed no statistically significant differences in mutation frequencies". This
statistically insignificant In statistical hypothesis testing A statistical hypothesis is a hypothesis that is testable on the basis of observed data modelled as the realised values taken by a collection of random variables. A set of data is modelled as being realised v ...
increase was also seen by independent researchers analyzing the children of the liquidators. Animal studies have shown that incomparably ''massive'' doses of X-ray irradiation of male mice resulted in birth defects of the offspring. In the 1980s, a relatively high prevalence of pediatric leukemia cases in children living near a nuclear processing plant in West Cumbria, UK, led researchers to investigate whether the cancer was a result of paternal radiation exposure. A significant association between paternal irradiation and offspring cancer was found, but further research areas close to other nuclear processing plants did not produce the same results. Later this was determined to be the Seascale cluster in which the leading hypothesis is the influx of foreign workers, who have a different rate of leukemia within their race than the British average, resulted in the observed cluster of 6 children more than expected around Cumbria.


Parent's age

Certain birth complications can occur more often in
advanced maternal age Advanced maternal age, in a broad sense, is the instance of a woman being of an older age at a stage of reproduction, although there are various definitions of specific age and stage of reproduction. Fathers contribute proportionally more DNA mutations to their offspring via their germ cells than the mother, with the paternal age governing how many mutations are passed on. This is because, as humans age, male germ cells acquire mutations at a much faster rate than female germ cells. Around a 5% increase in the incidence of ventricular septal defects, atrial septal defects, and
patent ductus arteriosus ''Patent ductus arteriosus'' (PDA) is a medical condition in which the ''ductus arteriosus The ductus arteriosus, also called the ductus Botalli, named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus c ...

patent ductus arteriosus
in offspring has been found to be correlated with advanced paternal age. Advanced paternal age has also been linked to increased risk of
achondroplasia Achondroplasia is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics, a genome is all genetic information of an organism. It ...
and
Apert syndrome Apert syndrome is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first Pharyngeal arch, branchial (or pharyng ...
. Offspring born to fathers under the age of 20 show increased risk of being affected by patent ductus arteriosus, ventricular septal defects, and the
tetralogy of Fallot Tetralogy of Fallot (TOF), formerly known as Steno-Fallot tetralogy, is a congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the hear ...

tetralogy of Fallot
. It is hypothesized that this may be due to environmental exposures or lifestyle choices. Research has found that there is a correlation between advanced paternal age and risk of birth defects such as limb anomalies, syndromes involving multiple systems, and
Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics Gen ...
. Recent studies have concluded that 5-9% of Down syndrome cases are due to paternal effects, but these findings are controversial. There is concrete evidence that advanced paternal age is associated with the increased likelihood that a mother will have a
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the natural loss of an embryo or fetus before it is fetal viability, able to survive independently. Some use the cutoff of 20 weeks of gestation, after whi ...
or that
fetal death Perinatal mortality (PNM) refers to the death of a fetus A fetus American and British English spelling differences#ae and oe, or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embr ...
will occur.


Unknown

Although significant progress has been made in identifying the etiology of some birth defects, approximately 65% have no known or identifiable cause. These are referred to as sporadic, a term that implies an unknown cause, random occurrence regardless of maternal living conditions, and a low recurrence risk for future children. For 20-25% of anomalies there seems to be a "multifactorial" cause, meaning a complex interaction of multiple minor genetic anomalies with environmental risk factors. Another 10–13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Only 12–25% of anomalies have a purely genetic cause. Of these, the majority are chromosomal anomalies.Kumar, Abbas and Fausto, eds., ''Robbins and Cotran's Pathologic Basis of Disease, 7th edition'', p.473.


Prevention

Folate supplements decrease the risk of neural tube defects. Tentative evidence supports the role of
L-arginine Arginine, also known as -arginine (symbol Arg or R), is an α-amino acid Amino acids are organic compounds that contain amino (–NH2) and Carboxylic acid, carboxyl (–COOH) functional groups, along with a Substituent, side chain (R group) s ...

L-arginine
in decreasing the risk of
intrauterine growth restriction Intrauterine growth restriction (IUGR) refers to poor growth of a fetus while in the mother's womb during pregnancy. The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus. At least ...
.


Screening

Newborn screening tests were introduced in the early 1960s and initially dealt with just two disorders. Since then
tandem mass spectrometry time-of-flight hybrid tandem mass spectrometer. Tandem mass spectrometry, also known as MS/MS or MS2, is a technique in instrumental analysis where two or more mass analyzers are coupled together using an additional reaction step to increase the ...
,
gas chromatography–mass spectrometry Gas chromatography–mass spectrometry (GC-MS) is an analytical method that combines the features of gas-chromatography and mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of io ...
, and DNA analysis has made it possible for a much larger range of disorders to be screened. Newborn screening mostly measures metabolite and enzyme activity using a dried blood spot sample. Screening tests are carried out in order to detect serious disorders that may be treatable to some extent. Early diagnosis makes possible the readiness of therapeutic dietary information, enzyme replacement therapy and organ transplants. Different countries support the screening for a number of metabolic disorders (
inborn errors of metabolismInborn errors of metabolism form a large class of genetic diseases involving congenital disorders of enzyme activities. The majority are due to defects of single genes that code for enzymes that facilitate conversion of various substances (substrate ...

inborn errors of metabolism
(IEM)), and genetic disorders including
cystic fibrosis Cystic fibrosis (CF) is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene In biology, a gene (from ''genos'' "...Wilhelm Johan ...
and
Duchenne muscular dystrophy Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis Th ...
. Tandem mass spectroscopy can also be used for IEM, and investigation of sudden infant death, and shaken baby syndrome. Screening can also be carried out prenatally and can include
obstetric ultrasonography ultrasonography, or prenatal ultrasound, is the use of in , in which sound waves are used to create real-time visual images of the developing or in the (womb). The procedure is a standard part of care in many countries, as it can provide a v ...
to give scans such as the nuchal scan. 3D ultrasound scans can give detailed information of structural anomalies.


Epidemiology

Congenital anomalies resulted in about 632,000 deaths per year in 2013 down from 751,000 in 1990. The types with the greatest death are
congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps ...
s (323,000), followed by
neural tube defects Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. ...
(69,000). Many studies have found that the frequency of occurrence of certain congenital malformations depends on the sex of the child (table). For example, pyloric stenosis occurs more often in males while congenital hip dislocation is four to five times more likely to occur in females. Among children with one kidney, there are approximately twice as many males, whereas among children with three kidneys there are approximately 2.5 times more females. The same pattern is observed among infants with excessive number of ribs, vertebrae, teeth and other organs which in a process of evolution have undergone reduction—among them there are more females. Contrarily, among the infants with their scarcity, there are more males. Anencephaly is shown to occur approximately twice as frequently in females.World Health Organization reports). "Congenital malformations", Geneve, 1966, p. 128. The number of boys born with 6 fingers is two times higher than the number of girls. Now various techniques are available to detect congenital anomalies in fetus before birth. About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance. Physical congenital abnormalities are the leading cause of infant mortality in the United States, accounting for more than 20% of all infant deaths. Seven to ten percent of all children will require extensive medical care to diagnose or treat a birth defect. : * Data obtained on opposite-sex twins. ** — Data were obtained in the period 1983–1994. P. M. Rajewski and A. L. Sherman (1976) have analyzed the frequency of congenital anomalies in relation to the system of the organism. Prevalence of men was recorded for the anomalies of phylogenetically younger organs and systems.Rajewski P. M., Sherman A. L. (1976) The importance of gender in the epidemiology of malignant tumors (systemic-evolutionary approach). In: Mathematical treatment of medical-biological information. M., Nauka, p. 170–181. In respect of an etiology, sexual distinctions can be divided on appearing before and after differentiation of male's gonads during embryonic development, which begins from eighteenth week. The testosterone level in male embryos thus raises considerably. The subsequent hormonal and physiological distinctions of male and female embryos can explain some sexual differences in frequency of congenital defects. It is difficult to explain the observed differences in the frequency of birth defects between the sexes by the details of the reproductive functions or the influence of environmental and social factors.


United States

The CDC and National Birth Defect Project studied the incidence of birth defects in the US. Key findings include: * Down syndrome was the most common condition with an estimated prevalence of 14.47 per 10,000 live births, implying about 6,000 diagnoses each year. * About 7,000 babies are born with a cleft palate, cleft lip or both.


See also

*
Malformative syndrome A malformative syndrome (or malformation syndrome) is a recognizable pattern of congenital anomalies that are known or thought to be causally related (VIIth International Congress on Human Genetics). Causes * exogenous causes ** exogenous tox ...
* ICD-10 Chapter Q: Congenital malformations, deformations and chromosomal abnormalities *
Idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...
*
List of congenital disordersList of congenital disorder A birth defect, also known as a congenital disorder, is a condition present at childbirth, birth regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, i ...
* List of ICD-9 codes 740-759: Congenital anomalies *
March of Dimes March of Dimes is a United States nonprofit organization A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, ...
*
Mitochondrial disease Mitochondrial disease is a group of disorders caused by mitochondrial dysfunction. Mitochondria A mitochondrion (; ) is a double-membrane Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selecti ...
*
Supernumerary body part An x-ray of a hand with a supernumerary digit (polydactyly) Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the human body, body and a deviation from the body plan. Body parts may be e ...


References


External links


CDC’s National Center on Birth Defects and Developmental Disabilities
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