The paternal age effect is the statistical relationship between the father's age at conception and biological effects on the child. Such effects can relate to

birthweight 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 weight ...

, congenital disorders, life expectancy and psychological outcomes. A 2017 review found that while severe health effects are associated with higher paternal age, the total increase in problems caused by paternal age is low. While paternal age has increased since 1960–1970, this is not seen as a major public health concern. The genetic quality of sperm, as well as its volume and motility, all may decrease with age, leading the population geneticist James F. Crow to claim that the "greatest mutational health hazard to the human genome is fertile older males". The paternal age effect was first proposed implicitly by physician

Wilhelm Weinberg Wilhelm Weinberg ( Stuttgart, 25 December 1862 – 27 November 1937, Tübingen) was a German obstetrician-gynecologist, practicing in Stuttgart, who in a 1908 paper, published in German in ''Jahresheft des Vereins für vaterländische Naturkun ...

in 1912 and explicitly by psychiatrist

Lionel Penrose Lionel Sharples Penrose, FRS (11 June 1898 – 12 May 1972) was an English psychiatrist, medical geneticist, paediatrician, mathematician and chess theorist, who carried out pioneering work on the genetics of intellectual disability. Penrose w ...

in 1955. DNA-based research started more recently, in 1998, in the context of paternity testing.

Health effects

Evidence for a paternal age effect has been proposed for a number of conditions, diseases and other effects. In many of these, the statistical evidence of association is weak, and the association may be related by

confounding In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Con ...

factors or behavioural differences. Conditions proposed to show correlation with paternal age include the following:

Single-gene disorders

Advanced paternal age may be associated with a higher risk for certain single-gene disorders caused by

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...

s of the ''

FGFR2 Fibroblast growth factor receptor 2 (FGFR2) also known as CD332 (cluster of differentiation 332) is a protein that in humans is encoded by the ''FGFR2'' gene residing on chromosome 10. FGFR2 is a receptor for fibroblast growth factor. The protein ...

'', ''

FGFR3 Fibroblast growth factor receptor 3 is a protein that in humans is encoded by the ''FGFR3'' gene. FGFR3 has also been designated as CD333 (cluster of differentiation 333). The gene, which is located on chromosome 4, location q16.3, is expressed in ...

'' and '' RET'' genes. These conditions are

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 branchial (or pharyngeal) arch, the ...

Crouzon syndrome Crouzon syndrome is an autosomal dominant genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial (or pharyngeal) arch, which is the precursor of the maxilla and mandible. Since the branchial ...

Pfeiffer syndrome Pfeiffer syndrome is a rare genetic disorder characterized by the premature fusion of certain bones of the skull (craniosynostosis) which affects the shape of the head and face. In addition, the syndrome includes abnormalities of the hands (such ...

achondroplasia Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism. In those with the condition, the arms and legs are short, while the torso is typically of normal length. Those affected ha ...

thanatophoric dysplasia Thanatophoric dysplasia is a severe skeletal disorder characterized by a disproportionately small ribcage, extremely short limbs and folds of extra skin on the arms and legs. Symptoms and signs Infants with this condition have disproportionately ...

multiple endocrine neoplasia type 2 Multiple endocrine neoplasia type 2 (also known as "Pheochromocytoma and amyloid producing medullary thyroid carcinoma", "PTC syndrome," and "Sipple syndrome") is a group of medical disorders associated with tumors of the endocrine system. The tum ...

, and multiple endocrine neoplasia type 2b. The most significant effect concerns achondroplasia (a form of

dwarfism Dwarfism is a condition wherein an organism is exceptionally small, and mostly occurs in the animal kingdom. In humans, it is sometimes defined as an adult height of less than , regardless of sex; the average adult height among people with dw ...

), which might occur in about 1 in 1,875 children fathered by men over 50, compared to 1 in 15,000 in the general population. However, the risk for achondroplasia is still considered clinically negligible. The '' FGFR'' genes may be particularly prone to a paternal age effect due to

selfish Selfishness is being concerned excessively or exclusively, for oneself or one's own advantage, pleasure, or welfare, regardless of others. Selfishness is the opposite of altruism or selflessness; and has also been contrasted (as by C. S. Lewis) w ...

spermatogonial selection, whereby the influence of spermatogonial mutations in older men is enhanced because cells with certain mutations have a selective advantage over other cells (see § DNA mutations).

Pregnancy effects

Several studies have reported that advanced paternal age is associated with an increased risk of

miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical lo ...

. The strength of the association differs between studies. It has been suggested that these miscarriages are caused by

chromosome abnormalities A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where ther ...

in the sperm of aging men. An increased risk for

stillbirth Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The term ...

has also been suggested for pregnancies fathered by men over 45.

Birth outcomes

systematic review A systematic review is a Literature review, scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from publ ...

published in 2010 concluded that the graph of the risk of low birthweight in infants with paternal age is "saucer-shaped" (U-shaped); that is, the highest risks occur at low and at high paternal ages. Compared with a paternal age of 25–28 years as a reference group, the odds ratio for low birthweight was approximately 1.1 at a paternal age of 20 and approximately 1.2 at a paternal age of 50. There was no association of paternal age with

preterm birth Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 we ...

s or with

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 ...

births.

Mental illness

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 withdra ...

is associated with advanced paternal age. Some studies examining

autism spectrum disorder The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental disorder, neurodevelopmental condition (or conditions) ...

(ASD) and advanced paternal age have demonstrated an association between the two, although there also appears to be an increase with

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. In one study, the risk of

bipolar disorder Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to weeks each. If the elevated mood is severe or associated with ...

, particularly for early-onset disease, is J-shaped, with the lowest risk for children of 20- to 24-year-old fathers, a twofold risk for younger fathers and a threefold risk for fathers >50 years old. There is no similar relationship with maternal age. A second study also found a risk of schizophrenia in both fathers above age 50 and fathers below age 25. The risk in younger fathers was noted to affect only male children. A 2010 study found the relationship between parental age and psychotic disorders to be stronger with maternal age than paternal age. A 2016 review concluded that the mechanism behind the reported associations was still not clear, with evidence both for

selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strategie ...

of individuals liable to psychiatric illness into late fatherhood and evidence for causative mutations. The mechanisms under discussion are not mutually exclusive. A 2017 review concluded that the vast majority of studies supported a relationship between older paternal age and autism and schizophrenia but that there is less convincing and also inconsistent evidence for associations with other psychiatric illnesses.

Cancers

Paternal age may be associated with an increased risk of

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

, but the association is weak and there are confounding effects. According to a 2017 review, there is consistent evidence of an increase in incidence of childhood

acute lymphoblastic leukemia Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruisin ...

with paternal age. Results for associations with other

childhood cancers Childhood cancer is cancer in a child. About 80% of childhood cancer cases can be successfully treated thanks to modern medical treatments and optimal patient care. However, only about 10% of children diagnosed with cancer reside in high-income cou ...

are more mixed (e.g.

retinoblastoma Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from the immature cells of a retina, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively fo ...

) or generally negative.

Diabetes mellitus

High paternal age has been suggested as a risk factor for

type 1 diabetes Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar for ...

, but research findings are inconsistent, and a clear association has not been established.

Down syndrome

It appears that a paternal-age effect might exist with respect to

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 ...

, but it is very small in comparison to the maternal-age effect.

Intelligence

A review in 2005 found a U-shaped relationship between paternal age and low

intelligence quotient An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. The abbreviation "IQ" was coined by the psychologist William Stern for the German term ''Intelligenzqu ...

s (IQs). The highest IQ was found at paternal ages of 25–29; fathers younger than 25 and older than 29 tended to have children with lower IQs. It also found that "at least a half dozen other studies ... have demonstrated significant associations between paternal age and human intelligence." A 2009 study examined children at 8 months, 4 years and 7 years and found that higher paternal age was associated with poorer scores in almost all

neurocognitive Neurocognitive functions are cognitive functions closely linked to the function of particular areas, neural pathways, or cortical networks in the brain, ultimately served by the substrate of the brain's neurological matrix (i.e. at the cellular ...

tests used but that higher maternal age was associated with better scores on the same tests; this was a reverse effect to that observed in the 2005 review, which found that maternal age began to correlate with lower intelligence at a younger age than paternal age, however two other past studies were in agreement with the 2009 study's results. An editorial accompanying the 2009 paper emphasized the importance of controlling for

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 studies of paternal age and intelligence. A 2010 study from Spain also found an association between advanced paternal age and intellectual disability. On the other hand, later research concluded that previously reported negative associations might be explained by confounding factors, especially parental intelligence and education. A re-analysis of the 2009 study found that the paternal age effect could be explained by adjusting for maternal education and number of siblings. A 2012 Scottish study found no significant association between paternal age and intelligence, after adjusting what was initially an inverse-U association for both parental education and socioeconomic status as well as number of siblings. A 2013 study of half a million Swedish men adjusted for genetic confounding by comparing brothers and found no association between paternal age and offspring IQ. Another study from 2014 found an initially positive association between paternal age and offspring IQ that disappeared when adjusting for parental IQs.

Life expectancy

A 2008 paper found a U-shaped association between paternal age and the overall mortality rate in children (i.e., mortality rate up to age 18). Although the relative mortality rates were higher, the absolute numbers were low, because of the relatively low occurrence of genetic abnormality. The study has been criticized for not adjusting for maternal health, which could have a large effect on child mortality. The researchers also found a correlation between paternal age and offspring death by injury or poisoning, indicating the need to control for social and behavioral confounding factors. In 2012, a study showed that greater age at paternity tends to increase

telomere A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature mos ...

length in offspring for up to two generations. Since telomere length has effects on health and mortality, this may have effects on health and the rate of aging in these offspring. The authors speculated that this effect may provide a mechanism by which populations have some plasticity in adapting longevity to different social and ecological contexts.

Fertility of the father

A 2001 review suggested older men have decreased pregnancy rates, increased time to pregnancy and increased

infertility Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal state ...

at a given point in time. When controlling for the age of the female partner, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rates between 23% and 38%.

Associated social and genetic characteristics

Parents do not decide when to reproduce randomly. This implies that paternal age effects may be

confounded In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Con ...

by social and genetic predictors of reproductive timing. A simulation study concluded that reported paternal age effects on psychiatric disorders in the epidemiological literature are too large to be explained only by mutations. They conclude that a model in which parents with a genetic liability to psychiatric illness tend to reproduce later better explains the literature. Later age at parenthood is also associated with a more stable family environment, with older parents being less likely to divorce or change partners. Older parents also tend to occupy a higher socio-economic position and report feeling more devoted to their children and satisfied with their family. On the other hand, the risk of the father dying before the child becomes an adult increases with paternal age. To adjust for genetic liability, some studies compare full siblings. Additionally, or alternatively, studies statistically adjust for some or all of these confounding factors. Using sibling comparisons or adjusting for more covariates frequently changes the direction or magnitude of paternal age effects. For example, one study drawing on Finnish census data concluded that increases in offspring mortality with paternal age could be explained completely by parental loss. On the other hand, a population-based cohort study drawing on 2.6 million records from Sweden found that risk of

attention deficit hyperactivity disorder Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...

was only positively associated with paternal age when comparing siblings.

Mechanisms

Several hypothesized chains of causality exist whereby increased paternal age may lead to health effects. There are different types of genome mutations, with distinct mutation mechanisms: *DNA length mutations of repetitive DNA (such as

s and

microsatellite A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from one to six or more base pairs) are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. ...

s), caused by cellular copying errors *DNA point mutations, caused by cellular copying errors and also by chemical and physical insults such as radiation *chromosome breaks and rearrangements, which can occur in the resting cell *epigenetic changes, i.e. methylation of the DNA, which can activate or silence certain genes, and is sometimes passed down from parent to child

Telomere length

Telomeres A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature mos ...

are repetitive genetic sequences at both ends of each chromosome that protect the structure of the

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

. As men age, most telomeres shorten, but sperm telomeres increase in length. The offspring of older fathers have longer telomeres in both their sperm and

white blood cells 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 ...

. A large study showed a positive paternal, but no independent maternal age effect on telomere length. Because the study used twins, it could not compare siblings who were discordant for paternal age. It found that telomere length was 70% heritable.

DNA point mutations

In contrast to

oogenesis Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. O ...

, the production of sperm cells is a lifelong process. Each year after puberty,

spermatogonia A spermatogonium (plural: ''spermatogonia'') is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testis. There are three subtypes of spermatogonia in humans: ...

(precursors of 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 chromosomes, ...

) divide meiotically about 23 times. By the age of 40, the spermatogonia will have undergone about 660 such divisions, compared to 200 at age 20. Copying errors might sometimes happen during the

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...

preceding these cell divisions, which may lead to new (''de novo'')

mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...

in the sperm DNA. The ''selfish spermatogonial selection'' hypothesis proposes that the influence of spermatogonial mutations in older men is further enhanced because cells with certain mutations have a selective advantage over other cells. Such an advantage would allow the mutated cells to increase in number through clonal expansion. In particular, mutations that affect the

RAS Ras or RAS may refer to: Arts and media * RAS Records Real Authentic Sound, a reggae record label * Rundfunk Anstalt Südtirol, a south Tyrolese public broadcasting service * Rás 1, an Icelandic radio station * Rás 2, an Icelandic radio stati ...

pathway, which regulates spermatogonial proliferation, appear to offer a competitive advantage to spermatogonial cells, while also leading to

diseases A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that ar ...

associated with paternal age.

Epigenetic changes

The production of sperm cells involves

DNA methylation DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts t ...

, an

epigenetic In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are "o ...

process that regulates the

expression of genes Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. Th ...

. Improper genomic imprinting and other errors sometimes occur during this process, which can affect the expression of genes related to certain disorders, increasing the offspring's susceptibility. The frequency of these errors appears to increase with age. This could explain the association between paternal age and schizophrenia.; Paternal age affects offspring's behavior, possibly via an epigenetic mechanism recruiting a transcriptional repressor REST.

Semen

A 2001 review on variation in semen quality and fertility by male age concluded that older men had lower semen volume, lower sperm motility, and a decreased percent of normal sperm. A 2014 review indicated that increasing male age is associated with declines in many semen traits, including semen volume and percentage motility. However, this review also found that sperm concentration did not decline as male age increased.

X-linked effects

Some classify the paternal age effect as one of two different types. One effect is directly related to advanced paternal age and autosomal mutations in the offspring. The other effect is an indirect effect in relation to mutations on the X chromosome which are passed to daughters who are then at risk for having sons with

X-linked Sex linked describes the sex-specific patterns of inheritance and presentation when a gene mutation (allele) is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). In humans, these are termed X-linked recessive, ...

diseases.

History

Birth defects were acknowledged in the children of older men and women even in antiquity. In book six of

Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...

Republic A republic () is a "state in which power rests with the people or their representatives; specifically a state without a monarchy" and also a "government, or system of government, of such a state." Previously, especially in the 17th and 18th c ...

Socrates Socrates (; ; –399 BC) was a Greek philosopher from Athens who is credited as the founder of Western philosophy and among the first moral philosophers of the ethical tradition of thought. An enigmatic figure, Socrates authored no te ...

states that men and women should have children in the "prime of their life" which is stated to be twenty in a woman and thirty in a man. He states that in his proposed society men should be forbidden to father children in their fifties and that the offspring of such unions should be considered "the offspring of darkness and strange lust." He suggests appropriate punishments be administered to the offenders and their offspring. In 1912,

, a German physician, was the first person to hypothesize that non-inherited cases of

could be more common in last-born children than in children born earlier to the same set of parents. Weinberg "made no distinction between paternal age, maternal age and

birth order Birth order refers to the order a child is born in their family; first-born and second-born are examples. Birth order is often believed to have a profound and lasting effect on psychological development. This assertion has been repeatedly challen ...

" in his hypothesis. In 1953, Krooth used the term "paternal age effect" in the context of achondroplasia, but mistakenly thought the condition represented a maternal age effect. The paternal age effect for achondroplasia was described by

in 1955. At a DNA level, the paternal age effect was first reported in 1998 in routine paternity tests. Scientific interest in paternal age effects is relevant because the average paternal age increased in countries such as the United Kingdom, Australia and Germany, and because birth rates for fathers aged 30–54 years have risen between 1980 and 2006 in the United States. Possible reasons for the increases in average paternal age include increasing life expectancy and increasing rates of divorce and remarriage. Despite recent increases in average paternal age, however, the oldest father documented in the medical literature was born in 1840: George Isaac Hughes was 94 years old at the time of the birth of his son by his second wife, a 1935 article in the ''

Journal of the American Medical Association ''The Journal of the American Medical Association'' (''JAMA'') is a peer-reviewed medical journal published 48 times a year by the American Medical Association. It publishes original research, reviews, and editorials covering all aspects of bio ...

'' stated that his fertility "has been definitely and affirmatively checked up medically," and he fathered a daughter in 1936 at age 96. In 2012, two 96-year-old men, Nanu Ram Jogi and Ramjit Raghav, both from India, claimed to have fathered children that year.

Medical assessment

The

American College of Medical Genetics The American College of Medical Genetics and Genomics (ACMG) is an organization composed of biochemical, clinical, cytogenetic, medical and molecular geneticists, genetic counselors and other health care professionals committed to the practice of ...

recommends

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 ...

at 18–20 weeks

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

in cases of advanced paternal age to evaluate fetal development, but it notes that this procedure "is unlikely to detect many of the conditions of interest." They also note that there is no standard definition of ''advanced paternal age''; it is commonly defined as age 40 or above, but the effect increases linearly with paternal age, rather than appearing at any particular age. According to a 2006 review, any adverse effects of advanced paternal age "should be weighed up against potential social advantages for children born to older fathers who are more likely to have progressed in their career and to have achieved financial security." Geneticist James F. Crow described mutations that have a direct visible effect on the child's health and also mutations that can be latent or have minor visible effects on the child's health; many such minor or latent mutations allow the child to reproduce, but cause more serious problems for grandchildren, great-grandchildren and later generations.

References

External links

* * * * * {{DEFAULTSORT:Paternal Age Effect Fatherhood Medical genetics Biology of bipolar disorder Senescence