Prenatal development () includes the development of the embryo and of the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

during a viviparous animal's gestation. Prenatal development starts with

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

, in the germinal stage of embryonic development, and continues in fetal development until

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 f ...

. In

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

pregnancy Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...

, prenatal development is also called antenatal development. The development of the human embryo follows

, and continues as

fetal development Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...

. By the end of the tenth week of

gestational age In obstetrics, gestational age is a measure of the age of a pregnancy which is taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. Su ...

the embryo has acquired its basic form and is referred to as a

. The next period is that of fetal development where many organs become fully developed. This fetal period is described both topically (by organ) and chronologically (by time) with major occurrences being listed by gestational age. The very early stages of embryonic development are the same in all mammals, but later stages of development, and the length of gestation varies.

Terminology

In the human: Different terms are used to describe prenatal development, meaning development before birth. A term with the same meaning is the "antepartum" (from Latin ''ante'' "before" and ''parere'' "to give birth") Sometimes "antepartum" is however used to denote the period between the 24th/26th week of gestational age until birth, for example in antepartum hemorrhage.patient.info » PatientPlus » Antepartum Haemorrhage
Last Updated: 5 May 2009 The perinatal period (from Greek ''peri'', "about, around" and Latin ''nasci'' "to be born") is "around the time of

". In

developed countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...

and at facilities where expert neonatal care is available, it is considered from 22 completed weeks (usually about 154 days) of gestation (the time when

birth weight Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is , with the normative range between . On average, babies of South Asian and Chinese descent weigh about . As far as low birth weigh ...

is normally 500 g) to 7 completed days after birth. In many of the

developing countries A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...

the starting point of this period is considered 28 completed weeks of gestation (or weight more than 1000 g).

Fertilization

Fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

marks the first

germinal stage Human embryonic development, or human embryogenesis, is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of de ...

of embryonic development. When

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Sem ...

is released into the

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

, the

spermatozoa A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromos ...

travel through the cervix, along the body of the

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...

, and into one of the fallopian tubes where fertilization usually takes place in the

ampulla An ampulla (; ) was, in Ancient Rome, a small round vessel, usually made of glass and with two handles, used for sacred purposes. The word is used of these in archaeology, and of later flasks, often handle-less and much flatter, for holy water or ...

. A great many sperm cells are released with the possibility of just one managing to adhere to and enter the thick protective layer surrounding the egg cell (ovum). The first sperm cell to successfully penetrate the egg cell donates its

genetic material Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main clas ...

( DNA) to combine with the DNA of the egg cell resulting in a new one-celled

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...

. The term "conception" refers variably to either fertilization or to formation of the

conceptus A conceptus (from Latin: ''concipere'' to conceive) is an embryo and its appendages (adnexa), the associated membranes, placenta, and umbilical cord; the products of conception or, more broadly, "the product of conception at any point between fert ...

after its implantation in the uterus, and this terminology is controversial. The zygote will develop into a male if the egg is fertilized by a sperm that carries a

Y chromosome The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abse ...

, or a female if the sperm carries an

X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...

. The Y chromosome contains a gene, '' SRY'', which will switch on

androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...

production at a later stage leading to the development of a

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

body type. In contrast, the mitochondrial DNA of the zygote comes entirely from the egg cell.

Development of the embryo

Following fertilization, the embryonic stage of development continues until the end of the 10th week (

) (8th week fertilization age). The first two weeks from fertilization is also referred to as the germinal stage or preembryonic stage. The

spends the next few days traveling down the fallopian tube dividing several times to form a ball of cells called a

morula A morula (Latin, ''morus'': mulberry) is an early-stage embryo consisting of a solid ball of cells called blastomeres, contained in mammals, and other animals within the zona pellucida shell. The blastomeres are the daughter cells of the zygot ...

. Further

cellular division Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there are ...

is accompanied by the formation of a small cavity between the cells. This stage is called a blastocyst. Up to this point there is no growth in the overall size of the embryo, as it is confined within a glycoprotein shell, known as the

zona pellucida The zona pellucida (plural zonae pellucidae, also egg coat or pellucid zone) is a specialized extracellular matrix that surrounds the plasma membrane of mammalian oocytes. It is a vital constitutive part of the oocyte. The zona pellucida first ap ...

. Instead, each division produces successively smaller cells. The blastocyst reaches the

at roughly the fifth day after fertilization. The blastocyst hatches from the zona pellucida allowing the blastocyst's outer cell layer of

trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the p ...

s to come into contact with, and adhere to, the

endometrial The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer ...

cells of the uterus. The trophoblasts will eventually give rise to extra-embryonic structures, such as the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

and the membranes. The embryo becomes embedded in the endometrium in a process called implantation. In most successful pregnancies, the embryo implants 8 to 10 days after ovulation. The embryo, the extra-embryonic membranes, and the placenta are collectively referred to as a conceptus, or the "products of conception". Rapid growth occurs and the embryo's main features begin to take form. This process is called differentiation, which produces the varied cell types (such as blood cells, kidney cells, and nerve cells). A spontaneous abortion, or miscarriage, in the

first trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...

of pregnancy is usually due to major genetic mistakes or abnormalities in the developing embryo. During this critical period the developing embryo is also susceptible to toxic exposures, such as: * Alcohol, certain drugs, and other toxins that cause

birth defect A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...

s, such as fetal alcohol syndrome *

Infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...

(such as rubella or cytomegalovirus) * Radiation from

x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

s or

radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...

Nutritional deficiencies Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues ...

such as lack 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 dietary supplement and in food fortification as it is more stable during processing an ...

which contributes to

spina bifida Spina bifida (Latin for 'split spine'; SB) is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy. There are three main types: spina bifida occulta, men ...

Nutrition

The embryo passes through 3 phases of acquisition of nutrition from the mother:Daftary, Shirish; Chakravarti, Sudip (2011). Manual of Obstetrics, 3rd Edition. Elsevier. pp. 1–16. . # ''Absorption phase:'' Zygote is nourished by cellular cytoplasm and secretions in fallopian tubes and uterine cavity. # ''Histoplasmic transfer:'' After nidation and before establishment of uteroplacental circulation, embryonic nutrition is derived from

decidual cells Before the fertilized ovum reaches the uterus, the mucous membrane of the body of the uterus undergoes important changes and is then known as the decidua. The thickness and vascularity of the mucous membrane are greatly increased; its glands are el ...

and maternal blood pools that open up as a result of eroding activity of

trophoblasts The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the ...

. # ''Hematotrophic phase:'' After third week of gestation, substances are transported passively via

intervillous space In the placenta, the intervillous space is the space between chorionic villi, and contains maternal blood. The trophoblast, which is a collection of cells that invades the maternal endometrium to gain access to nutrition for the fetus, prolif ...

Development of the fetus

The first ten weeks of

is the period of embryogenesis and together with the first three weeks of prenatal development make up the

of pregnancy. From the 10th week of gestation (8th week of development), the developing embryo is called a fetus. All major structures are formed by this time, but they continue to grow and develop. Because the precursors of the organs are now formed, the fetus is not as sensitive to damage from environmental exposure as the embryo was. Instead, toxic exposure often causes physiological abnormalities or minor congenital malformation.

Development of organ systems

Development continues throughout the life of the fetus and through into life after birth. Significant changes occur to many systems in the period after birth as they adapt to life outside the uterus.

Fetal blood

Hematopoiesis Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells ...

first takes place in the

yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is ...

. The function is transferred to the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

by the 10th week of gestation and to the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

and bone marrow beyond that. The total blood volume is about 125 ml/kg of fetal body weight near term.

Red blood cells

Megaloblastic red blood cells are produced early in development, which become normoblastic near term. Life span of prenatal RBCs is 80 days. Rh antigen appears at about 40 days of gestation.

White blood cells

The fetus starts producing

leukocytes White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

at 2 months gestational age, mainly from the

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

and the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

. Lymphocytes derived from the thymus are called

T lymphocyte A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...

s (T cells), whereas those derived from bone marrow are called

B lymphocytes B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or ...

(B cells). Both of these populations of lymphocytes have short-lived and long-lived groups. Short-lived T cells usually reside in thymus, bone marrow and spleen; whereas long-lived T cells reside in the blood stream.

Plasma cells Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B lymphocytes and secrete large quantities of proteins called antibodies in response to being presented specific substan ...

are derived from B cells and their life in fetal blood is 0.5 to 2 days.

Glands

The

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

is the first gland to develop in the embryo at the 4th week of gestation. Insulin secretion in the fetus starts around the 12th week of gestation.

Cognitive development

Electrical

brain activity Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...

is first detected at the end of week 5 of gestation, but as in

brain-dead Brain death is the permanent, irreversible, and complete loss of brain function which may include cessation of involuntary activity necessary to sustain life. It differs from persistent vegetative state, in which the person is alive and some au ...

patients, it is primitive neural activity rather than the beginning of conscious brain activity. Synapses don't begin to form until week 17. Neural connections between the sensory cortex and

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

develop as early as 24 weeks' gestational age, but the first evidence of their function does not occur until around 30 weeks, when minimal

consciousness Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...

dream A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, althou ...

ing, and the ability to feel pain emerges. Initial knowledge of the effects of prenatal experience on later neuropsychological development originates from the Dutch Famine Study, which researched the cognitive development of individuals born after the

Dutch famine of 1944–45 Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

. The first studies focused on the consequences of the famine to cognitive development, including the prevalence of intellectual disability.Stein, Z., Susser, M., Saenger, G., & Marolla, F. (1972). Nutrition and mental performance. Science, 178(62),708-713. Such studies predate David Barker's hypothesis about the association between the prenatal environment and the development of chronic conditions later in life. The initial studies found no association between malnourishment and cognitive development, but later studies found associations between malnourishment and increased risk for

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wit ...

, antisocial disorders, and affective disorders. There is evidence that the acquisition of language begins in the prenatal stage. After 26 weeks of gestation, the peripheral auditory system is already fully formed. Also, most low-frequency sounds (less than 300 Hz) can reach the fetal inner ear in the womb of mammals. Those low-frequency sounds include pitch, rhythm, and phonetic information related to language. Studies have indicated that fetuses react to and recognize differences between sounds. Such ideas are further reinforced by the fact that newborns present a preference for their mother's voice, present behavioral recognition of stories only heard during gestation, and (in monolingual mothers) present preference for their native language. A more recent study with

EEG Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...

demonstrated different brain activation in newborns hearing their native language compared to when they were presented with a different language, further supporting the idea that language learning starts while in gestation.

Growth rate

The growth rate of a fetus is linear up to 37 weeks of gestation, after which it plateaus. The growth rate of an embryo and infant can be reflected as the weight per

, and is often given as the weight put in relation to what would be expected by the gestational age. A baby born within the normal range of weight for that gestational age is known as appropriate for gestational age (AGA). An abnormally slow growth rate results in the infant being

small for gestational age Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age, most commonly defined as a weight below the 10th percentile for the gestational age. Causes Being small for gestational age is broadly ...

, while an abnormally large growth rate results in the infant being

large for gestational age Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term tha ...

. A slow growth rate and

preterm birth Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between 2 ...

are the two factors that can cause a

low birth weight Low birth weight (LBW) is defined by the World Health Organization as a birth weight of an infant of or less, regardless of gestational age. Infants born with LBW have added health risks which require close management, often in a neonatal inten ...

. Low birth weight (below 2000 grams) can slightly increase the likelihood of schizophrenia. The growth rate can be roughly correlated with the

fundal height Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development during pregnancy. It is measured from the top of the mother's uterus to the top of the mother's pubic symphysis. Fundal height, ...

of the uterus which can be estimated by abdominal palpation. More exact measurements can be performed with

obstetric ultrasonography Obstetric ultrasonography, or prenatal ultrasound, is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in the uterus (womb). The procedure is a stan ...

Factors influencing development

Intrauterine growth restriction Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...

is one of the causes of

associated with over half of

neonatal deaths Infant mortality is the death of young children under the age of 1. This death toll is measured by the infant mortality rate (IMR), which is the probability of deaths of children under one year of age per 1000 live births. The under-five morta ...

Poverty

Poverty has been linked to poor prenatal care and has been an influence on prenatal development. Women in poverty are more likely to have children at a younger age, which results in low birth weight. Many of these expecting mothers have little education and are therefore less aware of the risks of smoking, drinking alcohol, and drug use other factors that influence the growth rate of a fetus.

Mother's age

Women between the ages of 16 and 35 have a healthier environment for a fetus than women under 16 or over 35. Women between this age gap are more likely to have fewer complications. Women over 35 are more inclined to have a longer labor period, which could potentially result in death of the mother or fetus. Women under 16 and over 35 have a higher risk of preterm labor (premature baby), and this risk increases for women in poverty, women who take drugs, and women who smoke. Young mothers are more likely to engage in high risk behaviors, such as using alcohol, drugs, or smoking, resulting in negative consequences for the fetus. Premature babies from young mothers are more likely to have neurological defects that will influence their coping capabilities irritability, trouble sleeping, constant crying for example. There is an increased risk of

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...

for infants born to those aged over 40 years. Young teenaged mothers (younger than 16) and mothers over 35 are more exposed to the risks of miscarriages, premature births, and birth defects.

Drug use

An estimated 5 percent of fetuses in the United States are exposed to illicit drug use during pregnancy. Maternal drug use occurs when drugs ingested by the pregnant woman are metabolized in the placenta and then transmitted to the fetus. Recent research displays that there is a correlation between fine motor skills and prenatal risk factors such as the use of psychoactive substances and signs of abortion during pregnancy. As well as perinatal risk factors such as gestation time, duration of delivery, birth weight and postnatal risk factors such as constant falls.

Cannabis

When using

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternative ...

, there is a greater risk of birth defects, low birth weight, and a higher rate of death in infants or stillbirths. Drug use will influence extreme irritability, crying, and risk for

SIDS Sudden infant death syndrome (SIDS) is the sudden unexplained death of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough autopsy and detailed death scene investigation. SIDS usual ...

once the fetus is born. Marijuana will slow the fetal growth rate and can result in premature delivery. It can also lead to low birth weight, a shortened gestational period and complications in delivery. Cannabis use during pregnancy was unrelated to risk of perinatal death or need for special care, but, the babies of women who used cannabis at least once per week before and throughout pregnancy were 216g lighter than those of non‐users, had significantly shorter birth lengths and smaller head circumferences.

Opioids

Opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

s including heroin will cause interrupted fetal development, stillbirths, and can lead to numerous birth defects. Heroin can also result in premature delivery, creates a higher risk of miscarriages, result in facial abnormalities and head size, and create gastrointestinal abnormalities in the fetus. There is an increased risk for SIDS, dysfunction in the central nervous system, and neurological dysfunctions including tremors, sleep problems, and seizures. The fetus is also put at a great risk for low birth weight and respiratory problems.

Cocaine

Cocaine use results in a smaller brain, which results in learning disabilities for the fetus. Cocaine puts the fetus at a higher risk of being stillborn or premature. Cocaine use also results in low birthweight, damage to the central nervous system, and motor dysfunction. The vasoconstriction of the effects of cocaine lead to a decrease in placental blood flow to the fetus that results in fetal hypoxia (oxygen deficiency) and decreased fetal nutrition; these vasoconstrictive effects on the placenta have been linked to the number of complications in malformations that are evident in the newborn.

Methamphetamine

Prenatal methamphetamine exposure has shown to negatively impact brain development and behavioral functioning. A 2019 study further investigated neurocognitive and neurodevelopmental effects of prenatal methamphetamine exposure. This study had two groups, one containing children who were prenatally exposed to methamphetamine but no other illicit drugs and one containing children who met diagnosis criteria for ADHD but were not prenatally exposed to any illicit substance. Both groups of children completed intelligence measures to compute an IQ. Study results showed that the prenatally exposed children performed lower on the intelligence measures than their non-exposed peers with ADHD. The study results also suggest that prenatal exposure to methamphetamine may negatively impact processing speed as children develop.

Alcohol

Maternal alcohol use leads to disruptions of the fetus's brain development, interferes with the fetus's cell development and organization, and affects the maturation of the central nervous system. Even small amounts of alcohol use can cause lower height, weight and head size at birth and higher aggressiveness and lower intelligence during childhood. Fetal alcohol spectrum disorder is a developmental disorder that is a consequence of heavy alcohol intake by the mother during pregnancy. Children with FASD have a variety of distinctive facial features, heart problems, and cognitive problems such as developmental disabilities, attention difficulties, and memory deficits.

Tobacco use

Tobacco smoking Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or simply released from the mouth, as is generally done with pipes and cigars. The practice is believed ...

during pregnancy exposes the fetus to nicotine, tar, and

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

. Nicotine results in less blood flow to the fetus because it constricts the blood vessels. Carbon monoxide reduces the oxygen flow to the fetus. The reduction of blood and oxygen flow may result in miscarriage, stillbirth, low birth weight, and premature births. Exposure to secondhand smoke leads to higher risks of low birth weight and childhood cancer.

Infections

If a mother is infected with a disease, the placenta cannot always filter out the

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

Virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

es such as rubella,

chicken pox Chickenpox, also known as varicella, is a highly contagious disease caused by the initial infection with varicella zoster virus (VZV). The disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab ...

, mumps,

herpes Herpes simplex is a viral infection caused by the herpes simplex virus. Infections are categorized based on the part of the body infected. Oral herpes involves the face or mouth. It may result in small blisters in groups often called cold ...

, and

human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immun ...

(HIV) are associated with an increased risk of miscarriage,

, prematurity, physical malformations, and intellectual disabilities. HIV can lead to acquired immune deficiency syndrome (AIDS). Untreated HIV carries a risk of between 10 and 20 per cent of being passed on to the fetus. Bacterial or parasitic diseases may also be passed on to the fetus, and include

chlamydia Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium '' Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear they may occur only several we ...

, syphilis,

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, i ...

malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...

, and commonly

toxoplasmosis Toxoplasmosis is a parasitic disease caused by '' Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or mont ...

. Toxoplasmosis can be acquired through eating infected undercooked meat or contaminated food, and by drinking contaminated water. The risk of fetal infection is lowest during early pregnancy, and highest during the third trimester. However, in early pregnancy the outcome is worse, and can be fatal.

Maternal nutrition

Adequate nutrition is needed for a healthy fetus. Mothers who gain less than 20 pounds during pregnancy are at increased risk for having a preterm or low birth weight infant. Iron and iodine are especially important during prenatal development. Mothers who are deficient in iron are at risk for having a preterm or low birth weight infant. Iodine deficiencies increase the risk of miscarriage, stillbirth, and fetal brain abnormalities. Adequate

prenatal care Prenatal care, also known as antenatal care, is a type of preventive healthcare. It is provided in the form of medical checkups, consisting of recommendations on managing a healthy lifestyle and the provision of medical information such as materna ...

gives an improved result in the

newborn An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...

Low birth weight

Low birth weight Low birth weight (LBW) is defined by the World Health Organization as a birth weight of an infant of or less, regardless of gestational age. Infants born with LBW have added health risks which require close management, often in a neonatal inten ...

increases an infants risk of long-term growth and cognitive and language deficits. It also results in a shortened gestational period and can lead to prenatal complications.

Stress

Stress during pregnancy can have an impact the development of the embryo. Reilly (2017) states that stress can come from many forms of life events such as community, family, financial issues, and natural causes. While a woman is pregnant, stress from outside sources can take a toll on the growth in the womb that may affect the child's learning and relationships when born. For instance, they may have behavioral problems and might be antisocial. The stress that the mother experiences affects the fetus and the fetus' growth which can include the fetus' nervous system (Reilly, 2017). Stress can also lead to low birth weight. Even after avoiding other factors like alcohol, drugs, and being healthy, stress can have its impacts whether families know it or not. Many women who deal with maternal stress do not seek treatment. Similar to stress, Reilly stated that in recent studies, researchers have found that pregnant women who show depressive symptoms are not as attached and bonded to their child while it is in the womb (2017).

Environmental toxins

Exposure to

environmental toxins in pregnancy Environmental toxicants and fetal development is the impact of different toxic substances from the environment on the development of the fetus. This article deals with potential adverse effects of environmental toxicants on the prenatal development ...

lead to higher rates of miscarriage, sterility, and birth defects. Toxins include fetal exposure to lead, mercury, and ethanol or hazardous environments. Prenatal exposure to mercury may lead to physical deformation, difficulty in chewing and swallowing, and poor motoric coordination. Exposure to high levels of lead prenatally is related to prematurity, low birth weight, brain damage, and a variety of physical defects. Exposure to persistent

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...

from traffic and smog may lead to reduced infant head size, low birth weight, increased infant death rates, impaired lung and immune system development.

References

External links

Chart of human fetal development
U.S. National Library of Medicine (NLM)
U.K. Human Fertilisation and Embryology Authority (HFEA)
regulatory agency overseeing the use of gametes and embryos in fertility treatment and research {{DEFAULTSORT:Prenatal Development Embryology Fertility Midwifery