Birth defect

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This article is about congenital disorders in humans. Birth defect_sentence_0

For animals, see Teratology. Birth defect_sentence_1

Birth defect_table_infobox_0

Birth defectBirth defect_header_cell_0_0_0
Other namesBirth defect_header_cell_0_1_0 Congenital disorder, congenital disease, congenital deformity, congenital anomalyBirth defect_cell_0_1_1
SpecialtyBirth defect_header_cell_0_2_0 Medical genetics, pediatricsBirth defect_cell_0_2_1
SymptomsBirth defect_header_cell_0_3_0 Physical disability, intellectual disability, developmental disabilityBirth defect_cell_0_3_1
Usual onsetBirth defect_header_cell_0_4_0 Present at birthBirth defect_cell_0_4_1
TypesBirth defect_header_cell_0_5_0 Structural, functionalBirth defect_cell_0_5_1
CausesBirth defect_header_cell_0_6_0 Genetics, exposure to certain medications or chemicals, certain infections during pregnancyBirth defect_cell_0_6_1
Risk factorsBirth defect_header_cell_0_7_0 Insufficient folic acid, drinking alcohol or smoking, poorly controlled diabetes, mother over the age of 35Birth defect_cell_0_7_1
TreatmentBirth defect_header_cell_0_8_0 Therapy, medication, surgery, assistive technologyBirth defect_cell_0_8_1
FrequencyBirth defect_header_cell_0_9_0 3% of newborns (US)Birth defect_cell_0_9_1
DeathsBirth defect_header_cell_0_10_0 628,000 (2015)Birth defect_cell_0_10_1

A birth defect, also known as a congenital disorder, is a condition present at birth regardless of its cause. Birth defect_sentence_2

Birth defects may result in disabilities that may be physical, intellectual, or developmental. Birth defect_sentence_3

The disabilities can range from mild to severe. Birth defect_sentence_4

Birth defects are divided into two main types: structural disorders in which problems are seen with the shape of a body part and functional disorders in which problems exist with how a body part works. Birth defect_sentence_5

Functional disorders include metabolic and degenerative disorders. Birth defect_sentence_6

Some birth defects include both structural and functional disorders. Birth defect_sentence_7

Birth defects may result from genetic or chromosomal disorders, exposure to certain medications or chemicals, or certain infections during pregnancy. Birth defect_sentence_8

Risk factors include folate deficiency, drinking alcohol or smoking during pregnancy, poorly controlled diabetes, and a mother over the age of 35 years old. Birth defect_sentence_9

Many are believed to involve multiple factors. Birth defect_sentence_10

Birth defects may be visible at birth or diagnosed by screening tests. Birth defect_sentence_11

A number of defects can be detected before birth by different prenatal tests. Birth defect_sentence_12

Treatment varies depending on the defect in question. Birth defect_sentence_13

This may include therapy, medication, surgery, or assistive technology. Birth defect_sentence_14

Birth defects affected about 96 million people as of 2015. Birth defect_sentence_15

In the United States, they occur in about 3% of newborns. Birth defect_sentence_16

They resulted in about 628,000 deaths in 2015, down from 751,000 in 1990. Birth defect_sentence_17

The types with the greatest numbers of deaths are congenital heart disease (303,000), followed by neural tube defects (65,000). Birth defect_sentence_18

Classification Birth defect_section_0

Much of the language used for describing congenital conditions antedates genome mapping, and structural conditions are often considered separately from other congenital conditions. Birth defect_sentence_19

Many metabolic conditions are now known to have subtle structural expression, and structural conditions often have genetic links. Birth defect_sentence_20

Still, congenital conditions are often classified in a structural basis, organized when possible by primary organ system affected. Birth defect_sentence_21

Primarily structural Birth defect_section_1

Several terms are used to describe congenital abnormalities. Birth defect_sentence_22

(Some of these are also used to describe noncongenital conditions, and more than one term may apply in an individual condition.) Birth defect_sentence_23

Terminology Birth defect_section_2

Birth defect_unordered_list_0

  • 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), a third nipple, tiny indentations of the skin near the ears (preauricular pits), shortness of the fourth metacarpal or metatarsal bones, or dimples over the lower spine (sacral dimples). Some minor anomalies may be clues to more significant internal abnormalities.Birth defect_item_0_0
  • Birth defect is a widely used term for a congenital malformation, i.e. a congenital, physical anomaly that is recognizable at birth, and which is significant enough to be considered a problem. According to the Centers for Disease Control and Prevention (CDC), most birth defects are believed to be caused by a complex mix of factors including genetics, environment, and behaviors, though many birth defects have no known cause. An example of a birth defect is 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.Birth defect_item_0_1
  • 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.Birth defect_item_0_2
  • Some conditions are due to abnormal tissue development:Birth defect_item_0_3
    • A malformation is associated with a disorder of tissue development. Malformations often occur in the first trimester.Birth defect_item_0_4
    • A dysplasia is a disorder at the organ level that is due to problems with tissue development.Birth defect_item_0_5
  • Conditions also can arise after tissue is formed:Birth defect_item_0_6
    • A deformation 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.Birth defect_item_0_7
    • A disruption involves breakdown of normal tissues.Birth defect_item_0_8
  • When multiple effects occur in a specified order, they are known as a sequence. When the order is not known, it is a syndrome.Birth defect_item_0_9

Examples of primarily structural congenital disorders Birth defect_section_3

A limb anomaly is called a dysmelia. Birth defect_sentence_24

These include all forms of limbs anomalies, such as amelia, ectrodactyly, phocomelia, polymelia, polydactyly, syndactyly, polysyndactyly, oligodactyly, brachydactyly, achondroplasia, congenital aplasia or hypoplasia, amniotic band syndrome, and cleidocranial dysostosis. Birth defect_sentence_25

Congenital heart defects include patent ductus arteriosus, atrial septal defect, ventricular septal defect, and tetralogy of Fallot. Birth defect_sentence_26

Congenital anomalies of the nervous system include neural tube defects such as spina bifida, encephalocele, and anencephaly. Birth defect_sentence_27

Other congenital anomalies of the nervous system include the Arnold–Chiari malformation, the Dandy–Walker malformation, hydrocephalus, microencephaly, megalencephaly, lissencephaly, polymicrogyria, holoprosencephaly, and agenesis of the corpus callosum. Birth defect_sentence_28

Congenital anomalies of the gastrointestinal system include numerous forms of stenosis and atresia, and perforation, such as gastroschisis. Birth defect_sentence_29

Congenital anomalies of the kidney and urinary tract include renal parenchyma, kidneys, and urinary collecting system. Birth defect_sentence_30

Defects can be bilateral or unilateral, and different defects often coexist in an individual child. Birth defect_sentence_31

Primarily metabolic Birth defect_section_4

Main article: Inborn error of metabolism Birth defect_sentence_32

A congenital metabolic disease is also referred to as an inborn error of metabolism. Birth defect_sentence_33

Most of these are single-gene defects, usually heritable. Birth defect_sentence_34

Many affect the structure of body parts, but some simply affect the function. Birth defect_sentence_35

Other Birth defect_section_5

Other well-defined genetic conditions may affect the production of hormones, receptors, structural proteins, and ion channels. Birth defect_sentence_36

Causes Birth defect_section_6

Alcohol exposure Birth defect_section_7

Main articles: Fetal alcohol spectrum disorder and Fetal alcohol syndrome Birth defect_sentence_37

The mother's consumption of alcohol during pregnancy can cause a continuum of various permanent birth defects: cranofacial abnormalities, brain damage, intellectual disability, heart disease, kidney abnormality, skeletal anomalies, ocular abnormalities. Birth defect_sentence_38

The prevalence of children affected is estimated at least 1% in U.S. as well in Canada. Birth defect_sentence_39

Very few studies have investigated the links between paternal alcohol use and offspring health. Birth defect_sentence_40

However, recent animal research has shown a correlation between paternal alcohol exposure and decreased offspring birth weight. Birth defect_sentence_41

Behavioral and cognitive disorders, including difficulties with learning and memory, hyperactivity, and lowered stress tolerance have been linked to paternal alcohol ingestion. Birth defect_sentence_42

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 display because of maternal alcohol use. Birth defect_sentence_43

These birth defects and behavioral disorders were found in cases of both long- and short-term paternal alcohol ingestion. Birth defect_sentence_44

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 defects at birth. Birth defect_sentence_45

Toxic substances Birth defect_section_8

Further information: Developmental toxicity, Drugs in pregnancy, and Environmental toxins and fetal development Birth defect_sentence_46

Substances whose toxicity can cause congenital disorders are called teratogens, and include certain pharmaceutical and recreational drugs in pregnancy, as well as many environmental toxins in pregnancy. Birth defect_sentence_47

A review published in 2010 identified six main teratogenic mechanisms associated with medication use: folate antagonism, neural crest cell disruption, endocrine disruption, oxidative stress, vascular disruption, and specific receptor- or enzyme-mediated teratogenesis. Birth defect_sentence_48

An estimated 10% of all birth defects are caused by prenatal exposure to a teratogenic agent. Birth defect_sentence_49

These exposures include medication or drug exposures, maternal infections and diseases, and environmental and occupational exposures. Birth defect_sentence_50

Paternal smoking use 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. Birth defect_sentence_51

Teratogen-caused birth defects are potentially preventable. Birth defect_sentence_52

Nearly 50% of pregnant women have been exposed to at least one medication during gestation. Birth defect_sentence_53

During pregnancy, a woman can also be exposed to teratogens from the contaminated clothing or toxins within the seminal fluid of a partner. Birth defect_sentence_54

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. Birth defect_sentence_55

The United States Environmental Protection Agency studied 1,065 chemical and drug substances in their ToxCast program (part of the CompTox Chemicals Dashboard) using in silica modeling and a human pluripotent stem cell-based assay to predict in vivo developmental intoxicants based on changes in cellular metabolism following chemical exposure. Birth defect_sentence_56

Findings of the study published in 2020 were that 19% of the 1065 chemicals yielded a prediction of developmental toxicity. Birth defect_sentence_57

Medications and supplements Birth defect_section_9

Probably, the most well-known teratogenic drug is thalidomide. Birth defect_sentence_58

It was developed near the end of the 1950s by Chemie Grünenthal as a sleep-inducing aid and antiemetic. Birth defect_sentence_59

Because of its ability to prevent nausea, it was prescribed for pregnant women in almost 50 countries worldwide between 1956 and 1962. Birth defect_sentence_60

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. Birth defect_sentence_61

The most typical disorder induced by thalidomide were reductional deformities of the long bones of the extremities. Birth defect_sentence_62

Phocomelia, otherwise a rare deformity, therefore helped to recognise the teratogenic effect of the new drug. Birth defect_sentence_63

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. Birth defect_sentence_64

As thalidomide is used today as a treatment for multiple myeloma and leprosy, several births of affected children were described in spite of the strictly required use of contraception among female patients treated by it. Birth defect_sentence_65

Vitamin A is the sole vitamin that is embryotoxic even in a therapeutic dose, for example in multivitamins, because its metabolite, retinoic acid, plays an important role as a signal molecule in the development of several tissues and organs. Birth defect_sentence_66

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. Birth defect_sentence_67

Isotretinoin (13-cis-retinoic-acid; brand name Roaccutane), vitamin A analog, which is often used to treat severe acne, is such a strong teratogen that just a single dose taken by a pregnant woman (even transdermally) may result in serious birth defects. Birth defect_sentence_68

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. Birth defect_sentence_69

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. Birth defect_sentence_70

Vitamin A and similar substances can induce spontaneous abortions, premature births, defects of eyes (microphthalmia), ears, thymus, face deformities, and neurological (hydrocephalus, microcephalia) and cardiovascular defects, as well as mental retardation. Birth defect_sentence_71

Tetracycline, an antibiotic, should never be prescribed to women of reproductive age or to children, because of its negative impact on bone mineralization and teeth mineralization. Birth defect_sentence_72

The "tetracycline teeth" have brown or grey colour as a result of a defective development of both the dentine and the enamel of teeth. Birth defect_sentence_73

Several anticonvulsants are known to be highly teratogenic. Birth defect_sentence_74

Phenytoin, also known as diphenylhydantoin, along with carbamazepine, is responsible for the fetal hydantoin syndrome, which may typically include broad nose base, cleft lip and/or palate, microcephalia, nails and fingers hypoplasia, intrauterine growth restriction, and mental retardation. Birth defect_sentence_75

Trimethadione 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. Birth defect_sentence_76

Valproate has antifolate effects, leading to neural tube closure-related defects such as spina bifida. Birth defect_sentence_77

Lower IQ and autism have recently also been reported as a result of intrauterine valproate exposure. Birth defect_sentence_78

Hormonal contraception is considered as harmless for the embryo. Birth defect_sentence_79

Peterka and Novotná do, however, state that synthetic progestins used to prevent miscarriage in the past frequently caused masculinization of the outer reproductive organs of female newborns due to their androgenic activity. Birth defect_sentence_80

Diethylstilbestrol is a synthetic estrogen used from the 1940s to 1971, when the prenatal exposition has been linked to the clear-cell adenocarcinoma of the vagina. Birth defect_sentence_81

Following studies showed elevated risks for other tumors and congenital malformations of the sex organs for both sexes. Birth defect_sentence_82

All cytostatics are strong teratogens; abortion is usually recommended when pregnancy is discovered during or before chemotherapy. Birth defect_sentence_83

Aminopterin, a cytostatic drug with antifolate effect, was used during the 1950s and 1960s to induce therapeutic abortions. Birth defect_sentence_84

In some cases, the abortion did not happen, but the newborns suffered a fetal aminopterin syndrome consisting of growth retardation, craniosynostosis, hydrocephalus, facial dismorphities, mental retardation, and/or leg deformities Birth defect_sentence_85

Toxic substances Birth defect_section_10

Drinking water is often a medium through which harmful toxins travel. Birth defect_sentence_86

Heavy metals, elements, nitrates, nitrites, and fluoride can be carried through water and cause congenital disorders. Birth defect_sentence_87

Nitrate, which is found mostly in drinking water from ground sources, is a powerful teratogen. Birth defect_sentence_88

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. Birth defect_sentence_89

Chlorinated and aromatic solvents such as benzene and trichloroethylene sometimes enter the water supply due to oversights in waste disposal. Birth defect_sentence_90

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. Birth defect_sentence_91

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. Birth defect_sentence_92

As an endocrine disruptor, DDT was shown to induce miscarriages, interfere with the development of the female reproductive system, cause the congenital hypothyroidism, and suspectibly childhood obesity. Birth defect_sentence_93

Fluoride, when transmitted through water at high levels, can also act as a teratogen. Birth defect_sentence_94

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. Birth defect_sentence_95

In studies conducted on rats, higher fluoride in drinking water led to increased acetylcholinesterase levels, which can alter prenatal brain development. Birth defect_sentence_96

The most significant effects were noted at a level of 5 ppm. Birth defect_sentence_97

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. Birth defect_sentence_98

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. Birth defect_sentence_99

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. Birth defect_sentence_100

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. Birth defect_sentence_101

The effect of chronic exposure to carbon monoxide can depend on the stage of pregnancy in which the mother is exposed. Birth defect_sentence_102

Exposure during the embryonic stage can have neurological consequences, such as telencephalic dysgenesis, behavioral difficulties during infancy, and reduction of cerebellum volume. Birth defect_sentence_103

Also, possible skeletal defects could result from exposure to carbon monoxide during the embryonic stage, such as hand and foot malformations, hip dysplasia, hip subluxation, agenesis of a limb, and inferior maxillary atresia with glossoptosis. Birth defect_sentence_104

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. Birth defect_sentence_105

Exposure to carbon monoxide or polluted ozone exposure can also lead to cardiac defects of the ventrical septal, pulmonary artery, and heart valves. Birth defect_sentence_106

The effects of carbon monoxide exposure are decreased later in fetal development during the fetal stage, but they may still lead to anoxic encephalopathy. Birth defect_sentence_107

Industrial pollution can also lead to congenital defects. Birth defect_sentence_108

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. Birth defect_sentence_109

This led to many people in the area to develop what became known as the "Minamata disease". Birth defect_sentence_110

Because methylmercury is a teratogen, the mercury poisoning of those residing by the bay resulted in neurological defects in the offspring. Birth defect_sentence_111

Infants exposed to mercury poisoning in utero showed predispositions to cerebral palsy, ataxia, inhibited psychomotor development, and mental retardation. Birth defect_sentence_112

Landfill sites have been shown to have adverse effects on fetal development. Birth defect_sentence_113

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. Birth defect_sentence_114

Studies done around the Love Canal 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. Birth defect_sentence_115

A study done in California showed a positive correlation between time and quantity of dumping and low birth weights and neonatal deaths. Birth defect_sentence_116

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, epispadia, and abdominal wall defects, such as gastroschisis and exomphalos. Birth defect_sentence_117

A study conducted on a Welsh community also showed an increase incidence of gastroschisis. Birth defect_sentence_118

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. Birth defect_sentence_119

These birth defects included neural tube defects, malformations of the cardiac septa, anomalies of arteries and veins, and chromosomal anomalies. Birth defect_sentence_120

Looking at communities that live near landfill sites brings up environmental justice. Birth defect_sentence_121

A vast majority of sites are located near poor, mostly black, communities. Birth defect_sentence_122

For example, between the early 1920s and 1978, about 25% of Houston's population was black. Birth defect_sentence_123

However, over 80% of landfills and incinerators during this time were located in these black communities. Birth defect_sentence_124

Another issue regarding environmental justice is lead poisoning. Birth defect_sentence_125

A fetus exposed to lead during the pregnancy can result in learning difficulties and slowed growth. Birth defect_sentence_126

Some paints (before 1978) and pipes contain lead. Birth defect_sentence_127

Therefore, pregnant women who live in homes with lead paint inhale the dust containing lead, leading to lead exposure in the fetus. Birth defect_sentence_128

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. Birth defect_sentence_129

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. Birth defect_sentence_130

Smoking Birth defect_section_11

Paternal smoking prior to conception has been linked with the increased risk of congenital abnormalities in offspring. Birth defect_sentence_131

Smoking causes DNA mutations in the germline of the father, which can be inherited by the offspring. Birth defect_sentence_132

Cigarette smoke acts as a chemical mutagen on germ cell DNA. Birth defect_sentence_133

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. Birth defect_sentence_134

This oxidative damage may result in epigenetic or genetic modifications of the father's germline. Birth defect_sentence_135

Fetal lymphocytes have been damaged as a result of a father's smoking habits prior to conception. Birth defect_sentence_136

Correlations between paternal smoking and the increased risk of offspring developing childhood cancers (including acute leukemia, brain tumors, and lymphoma) before age five have been established. Birth defect_sentence_137

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. Birth defect_sentence_138

Infections Birth defect_section_12

Main article: Vertically transmitted infection Birth defect_sentence_139

A vertically transmitted infection is an infection caused by bacteria, viruses, or in rare cases, parasites transmitted directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth. Birth defect_sentence_140

Congenital disorders were initially believed to be the result of only hereditary factors. Birth defect_sentence_141

However, in the early 1940s, Australian pediatric ophthalmologist 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. Birth defect_sentence_142

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. Birth defect_sentence_143

These findings confirmed, to Gregg, that, in fact, environmental causes for congenital disorders could exist. Birth defect_sentence_144

Rubella is known to cause abnormalities of the eye, internal ear, heart, and sometimes the teeth. Birth defect_sentence_145

More specifically, fetal exposure to rubella during weeks five to ten of development (the sixth week particularly) can cause cataracts and microphthalmia in the eyes. Birth defect_sentence_146

If the mother is infected with rubella during the ninth week, a crucial week for internal ear development, destruction of the organ of Corti can occur, causing deafness. Birth defect_sentence_147

In the heart, the ductus arteriosus can remain after birth, leading to hypertension. Birth defect_sentence_148

Rubella can also lead to atrial and ventricular septal defects in the heart. Birth defect_sentence_149

If exposed to rubella in the second trimester, the fetus can develop central nervous system malformations. Birth defect_sentence_150

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. Birth defect_sentence_151

The timing of the mother's infection during fetal development determines the risk and type of birth defect. Birth defect_sentence_152

As the embryo develops, the risk of abnormalities decreases. Birth defect_sentence_153

If exposed to the rubella virus during the first four weeks, the risk of malformations is 47%. Birth defect_sentence_154

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. Birth defect_sentence_155

Exposure during the first eight weeks of development can also lead to premature birth and fetal death. Birth defect_sentence_156

These numbers are calculated from immediate inspection of the infant after birth. Birth defect_sentence_157

Therefore, mental defects are not accounted for in the percentages because they are not evident until later in the child's life. Birth defect_sentence_158

If they were to be included, these numbers would be much higher. Birth defect_sentence_159

Other infectious agents include cytomegalovirus, the herpes simplex virus, hyperthermia, toxoplasmosis, and syphilis. Birth defect_sentence_160

Maternal exposure to cytomegalovirus can cause microcephaly, cerebral calcifications, blindness, chorioretinitis (which can cause blindness), hepatosplenomegaly, and meningoencephalitis in fetuses. Birth defect_sentence_161

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. Birth defect_sentence_162

All three disorders cause abnormal brain function or mental retardation. Birth defect_sentence_163

Hepatosplenomegaly is the enlargement of the liver and spleen which causes digestive problems. Birth defect_sentence_164

It can also cause some kernicterus and petechiae. Birth defect_sentence_165

Kernicterus causes yellow pigmentation of the skin, brain damage, and deafness. Birth defect_sentence_166

Petechaie is when the capillaries bleed resulting in red/purple spots on the skin. Birth defect_sentence_167

However, cytomegalovirus is often fatal in the embryo. Birth defect_sentence_168

The herpes simplex virus can cause microcephaly, microphthalmus (abnormally small eyeballs), retinal dysplasia, hepatosplenomegaly, and mental retardation. Birth defect_sentence_169

Both microphthalmus and retinal dysplasia can cause blindness. Birth defect_sentence_170

However, the most common symptom in infants is an inflammatory response that develops during the first three weeks of life. Birth defect_sentence_171

Hyperthermia causes anencephaly, which is when part of the brain and skull are absent in the infant. Birth defect_sentence_172

Mother exposure to toxoplasmosis can cause cerebral calcification, hydrocephalus (causes mental disabilities), and mental retardation in infants. Birth defect_sentence_173

Other birth abnormalities have been reported as well, such as chorioretinitis, microphthalmus, and ocular defects. Birth defect_sentence_174

Syphilis causes congenital deafness, mental retardation, and diffuse fibrosis in organs, such as the liver and lungs, if the embryo is exposed. Birth defect_sentence_175

Lack of nutrients Birth defect_section_13

Further information: Nutrition in pregnancy and Folate deficiency Birth defect_sentence_176

For example, a lack of folic acid, a B vitamin, in the diet of a mother can cause cellular neural tube deformities that result in spina bifida. Birth defect_sentence_177

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. Birth defect_sentence_178

Folic acid, or vitamin B9, aids the development of the foetal nervous system. Birth defect_sentence_179

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. Birth defect_sentence_180

Physical restraint Birth defect_section_14

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. Birth defect_sentence_181

An example is Potter syndrome due to oligohydramnios. Birth defect_sentence_182

This finding is important for future understanding of how genetics may predispose individuals for diseases such as obesity, diabetes, and cancer. Birth defect_sentence_183

For multicellular organisms that develop in a womb, the physical interference or presence of other similarly developing organisms such as 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. Birth defect_sentence_184

The two cellular masses can compete with each other, and may either duplicate or merge various structures. Birth defect_sentence_185

This results in conditions such as conjoined twins, 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. Birth defect_sentence_186

Genetics Birth defect_section_15

Main article: Genetic disorder Birth defect_sentence_187

See also: List of genetic disorders Birth defect_sentence_188

Genetic causes of birth defects include inheritance of abnormal genes from the mother or the father, as well as new mutations in one of the germ cells that gave rise to the fetus. Birth defect_sentence_189

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. Birth defect_sentence_190

If an egg is fertilized with sperm that has damaged DNA, a possibility exists that the fetus could develop abnormally. Birth defect_sentence_191

Genetic disorders are all congenital (present at birth), though they may not be expressed or recognized until later in life. Birth defect_sentence_192

Genetic disorders may be grouped into single-gene defects, multiple-gene disorders, or chromosomal defects. Birth defect_sentence_193

Single-gene defects may arise from abnormalities of both copies of an autosomal gene (a recessive disorder) or of only one of the two copies (a dominant disorder). Birth defect_sentence_194

Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Birth defect_sentence_195

Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Birth defect_sentence_196

Large chromosomal abnormalities always produce effects on many different body parts and organ systems. Birth defect_sentence_197

Socioeconomics Birth defect_section_16

A low socioeconomic status in a deprived neighborhood may include exposure to "environmental stressors and risk factors". Birth defect_sentence_198

Socioeconomic inequalities are commonly measured by the Cartairs-Morris score, Index of Multiple Deprivation, Townsend deprivation index, and the Jarman score. Birth defect_sentence_199

The Jarman score, for example, considers "unemployment, overcrowding, single parents, under-fives, elderly living alone, ethnicity, low social class and residential mobility". Birth defect_sentence_200

In Vos’ meta-analysis these indices are used to view the effect of low SES neighborhoods on maternal health. Birth defect_sentence_201

In the meta-analysis, data from individual studies were collected from 1985 up until 2008. Birth defect_sentence_202

Vos concludes that a correlation exists between prenatal adversities and deprived neighborhoods. Birth defect_sentence_203

Other studies have shown that low SES is closely associated with the development of the fetus in utero and growth retardation. Birth defect_sentence_204

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". Birth defect_sentence_205

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)". Birth defect_sentence_206

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. Birth defect_sentence_207

After controlling for socioeconomic factors and ethnicity, several individual studies demonstrated an association with outcomes such as perinatal mortality and preterm birth. Birth defect_sentence_208

Radiation Birth defect_section_17

For the survivors of the atomic bombing of Hiroshima and Nagasaki, who are known as the 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. Birth defect_sentence_209

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. Birth defect_sentence_210

Relatively few studies have researched the effects of paternal radiation exposure on offspring. Birth defect_sentence_211

Following the Chernobyl disaster, it was assumed in the 1990s that the germ line of irradiated fathers suffered minisatellite mutations in the DNA, which was inherited by descendants. Birth defect_sentence_212

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". Birth defect_sentence_213

This statistically insignificant increase was also seen by independent researchers analyzing the children of the liquidators. Birth defect_sentence_214

Animal studies have shown that incomparably massive doses of X-ray irradiation of male mice resulted in birth defects of the offspring. Birth defect_sentence_215

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. Birth defect_sentence_216

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. Birth defect_sentence_217

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. Birth defect_sentence_218

Parent's age Birth defect_section_18

Main articles: Advanced maternal age and Paternal age effect Birth defect_sentence_219

Certain birth complications can occur more often in advanced maternal age (greater than 35 years). Birth defect_sentence_220

Complications include fetal growth restriction, preeclampsia, placental abruption, pre-mature births, and stillbirth. Birth defect_sentence_221

These complications not only may put the child at risk, but also the mother. Birth defect_sentence_222

The effects of the father's age on offspring are not yet well understood and are studied far less extensively than the effects of the mother's age. Birth defect_sentence_223

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. Birth defect_sentence_224

This is because, as humans age, male germ cells acquire mutations at a much faster rate than female germ cells. Birth defect_sentence_225

Around a 5% increase in the incidence of ventricular septal defects, atrial septal defects, and patent ductus arteriosus in offspring has been found to be correlated with advanced paternal age. Birth defect_sentence_226

Advanced paternal age has also been linked to increased risk of achondroplasia and Apert syndrome. Birth defect_sentence_227

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. Birth defect_sentence_228

It is hypothesized that this may be due to environmental exposures or lifestyle choices. Birth defect_sentence_229

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. Birth defect_sentence_230

Recent studies have concluded that 5-9% of Down syndrome cases are due to paternal effects, but these findings are controversial. Birth defect_sentence_231

There is concrete evidence that advanced paternal age is associated with the increased likelihood that a mother will have a miscarriage or that fetal death will occur. Birth defect_sentence_232

Unknown Birth defect_section_19

Although significant progress has been made in identifying the etiology of some birth defects, approximately 65% have no known or identifiable cause. Birth defect_sentence_233

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. Birth defect_sentence_234

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. Birth defect_sentence_235

Another 10–13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Birth defect_sentence_236

Only 12–25% of anomalies have a purely genetic cause. Birth defect_sentence_237

Of these, the majority are chromosomal anomalies. Birth defect_sentence_238

Prevention Birth defect_section_20

Folate supplements decrease the risk of neural tube defects. Birth defect_sentence_239

Tentative evidence supports the role of L-arginine in decreasing the risk of intrauterine growth restriction. Birth defect_sentence_240

Screening Birth defect_section_21

Main article: Newborn screening Birth defect_sentence_241

Newborn screening tests were introduced in the early 1960s and initially dealt with just two disorders. Birth defect_sentence_242

Since then tandem mass spectrometry, gas chromatography–mass spectrometry, and DNA analysis has made it possible for a much larger range of disorders to be screened. Birth defect_sentence_243

Newborn screening mostly measures metabolite and enzyme activity using a dried blood spot sample. Birth defect_sentence_244

Screening tests are carried out in order to detect serious disorders that may be treatable to some extent. Birth defect_sentence_245

Early diagnosis makes possible the readiness of therapeutic dietary information, enzyme replacement therapy and organ transplants. Birth defect_sentence_246

Different countries support the screening for a number of metabolic disorders (inborn errors of metabolism (IEM)), and genetic disorders including cystic fibrosis and Duchenne muscular dystrophy. Birth defect_sentence_247

Tandem mass spectroscopy can also be used for IEM, and investigation of sudden infant death, and shaken baby syndrome. Birth defect_sentence_248

Screening can also be carried out prenatally and can include obstetric ultrasonography to give scans such as the nuchal scan. Birth defect_sentence_249

3D ultrasound scans can give detailed information of structural anomalies. Birth defect_sentence_250

Epidemiology Birth defect_section_22

Congenital anomalies resulted in about 632,000 deaths per year in 2013 down from 751,000 in 1990. Birth defect_sentence_251

The types with the greatest death are congenital heart defects (323,000), followed by neural tube defects (69,000). Birth defect_sentence_252

Many studies have found that the frequency of occurrence of certain congenital malformations depends on the sex of the child (table). Birth defect_sentence_253

For example, pyloric stenosis occurs more often in males while congenital hip dislocation is four to five times more likely to occur in females. Birth defect_sentence_254

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. Birth defect_sentence_255

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. Birth defect_sentence_256

Contrarily, among the infants with their scarcity, there are more males. Birth defect_sentence_257

Anencephaly is shown to occur approximately twice as frequently in females. Birth defect_sentence_258

The number of boys born with 6 fingers is two times higher than the number of girls. Birth defect_sentence_259

Now various techniques are available to detect congenital anomalies in fetus before birth. Birth defect_sentence_260

About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance. Birth defect_sentence_261

Physical congenital abnormalities are the leading cause of infant mortality in the United States, accounting for more than 20% of all infant deaths. Birth defect_sentence_262

Seven to ten percent of all children will require extensive medical care to diagnose or treat a birth defect. Birth defect_sentence_263

Birth defect_description_list_1

  • The sex ratio of patients with congenital malformations Congenital anomaly Sex ratio, ♂♂:♀♀ Defects with female predominance Congenital hip dislocation 1 : 5.2; 1 : 5; 1 : 8; 1 : 3.7 Cleft palate 1 : 3 Anencephaly 1 : 1.9; 1 : 2 Craniocele 1 : 1.8 Aplasia of lung 1 : 1.51 Spinal herniation 1 : 1.4 Diverticulum of the esophagus 1 : 1.4 Stomach 1 : 1.4 Neutral defects Hypoplasia of the tibia and femur 1 : 1.2 Spina bifida 1 : 1.2 Atresia of small intestine 1 : 1 Microcephaly 1.2 : 1 Esophageal atresia 1.3 : 1; 1.5 : 1 Hydrocephalus 1.3 : 1 Defects with male predominance Diverticula of the colon 1.5 : 1 Atresia of the rectum 1.5 : 1; 2 : 1 Unilateral renal agenesis 2 : 1; 2.1 : 1 Schistocystis 2 : 1 Cleft lip and palate 2 : 1; 1.47 : 1 Bilateral renal agenesis 2.6 : 1 Congenital anomalies of the genitourinary system 2.7 : 1 Pyloric stenosis, congenital 5 : 1; 5.4 : 1 Meckel's diverticulum More common in boys Congenital megacolon More common in boys All defects 1.22 : 1; 1.29 : 1Birth defect_item_1_10

Birth defect_unordered_list_2

  • Data obtained on opposite-sex twins. ** — Data were obtained in the period 1983–1994.Birth defect_item_2_11

P. M. Rajewski and A. L. Sherman (1976) have analyzed the frequency of congenital anomalies in relation to the system of the organism. Birth defect_sentence_264

Prevalence of men was recorded for the anomalies of phylogenetically younger organs and systems. Birth defect_sentence_265

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. Birth defect_sentence_266

The testosterone level in male embryos thus raises considerably. Birth defect_sentence_267

The subsequent hormonal and physiological distinctions of male and female embryos can explain some sexual differences in frequency of congenital defects. Birth defect_sentence_268

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. Birth defect_sentence_269

United States Birth defect_section_23

The CDC and National Birth Defect Project studied the incidence of birth defects in the US. Birth defect_sentence_270

Key findings include: Birth defect_sentence_271

Birth defect_unordered_list_3

  • 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.Birth defect_item_3_12
  • About 7,000 babies are born with a cleft palate, cleft lip or both.Birth defect_item_3_13

Birth defect_table_general_1

Adjusted National Prevalence Estimates and Estimated Number of Cases in the United States, 2004–2006Birth defect_table_caption_1
Birth DefectsBirth defect_header_cell_1_0_0 Cases per BirthsBirth defect_header_cell_1_0_1 Estimated Annual Number of CasesBirth defect_header_cell_1_0_2 Estimated National Prevalence per 10,000 Live Births (Adjusted for maternal race/ethnicity)Birth defect_header_cell_1_0_3
Central nervous system defectsBirth defect_cell_1_1_0
AnencephalyBirth defect_cell_1_2_0 1 in 4,859Birth defect_cell_1_2_1 859Birth defect_cell_1_2_2 2.06Birth defect_cell_1_2_3
Spina bifida without anencephalyBirth defect_cell_1_3_0 1 in 2,858Birth defect_cell_1_3_1 1460Birth defect_cell_1_3_2 3.50Birth defect_cell_1_3_3
EncephaloceleBirth defect_cell_1_4_0 1 in 12,235Birth defect_cell_1_4_1 341Birth defect_cell_1_4_2 0.82Birth defect_cell_1_4_3
Eye defectsBirth defect_cell_1_5_0
Anophthalmia/ microphthalmiaBirth defect_cell_1_6_0 1 in 5,349Birth defect_cell_1_6_1 780Birth defect_cell_1_6_2 1.87Birth defect_cell_1_6_3
Cardiovascular defectsBirth defect_cell_1_7_0
Common truncusBirth defect_cell_1_8_0 1 in 13,876Birth defect_cell_1_8_1 301Birth defect_cell_1_8_2 0.72Birth defect_cell_1_8_3
Transposition of great arteriesBirth defect_cell_1_9_0 1 in 3,333Birth defect_cell_1_9_1 1252Birth defect_cell_1_9_2 3.00Birth defect_cell_1_9_3
Tetralogy of FallotBirth defect_cell_1_10_0 1 in 2,518Birth defect_cell_1_10_1 1657Birth defect_cell_1_10_2 3.97Birth defect_cell_1_10_3
Atrioventricular septal defectBirth defect_cell_1_11_0 1 in 2,122Birth defect_cell_1_11_1 1966Birth defect_cell_1_11_2 4.71Birth defect_cell_1_11_3
Hypoplastic left heart syndromeBirth defect_cell_1_12_0 1 in 4,344Birth defect_cell_1_12_1 960Birth defect_cell_1_12_2 2.30Birth defect_cell_1_12_3
Orofacial defectsBirth defect_cell_1_13_0
Cleft palate without cleft lipBirth defect_cell_1_14_0 1 in 1,574Birth defect_cell_1_14_1 2651Birth defect_cell_1_14_2 6.35Birth defect_cell_1_14_3
Cleft lip with and without cleft palateBirth defect_cell_1_15_0 1 in 940Birth defect_cell_1_15_1 4437Birth defect_cell_1_15_2 10.63Birth defect_cell_1_15_3
Gastrointestinal defectsBirth defect_cell_1_16_0
Esophageal atresia/tracheoeophageal fistulaBirth defect_cell_1_17_0 1 in 4,608Birth defect_cell_1_17_1 905Birth defect_cell_1_17_2 2.17Birth defect_cell_1_17_3
Rectal and large intestinalatresia/stenosisBirth defect_cell_1_18_0 1 in 2,138Birth defect_cell_1_18_1 1952Birth defect_cell_1_18_2 4.68Birth defect_cell_1_18_3
Musculoskeletal defectsBirth defect_cell_1_19_0
Reduction deformity, upper limbsBirth defect_cell_1_20_0 1 in 2,869Birth defect_cell_1_20_1 1454Birth defect_cell_1_20_2 3.49Birth defect_cell_1_20_3
Reduction deformity, lower limbsBirth defect_cell_1_21_0 1 in 5,949Birth defect_cell_1_21_1 701Birth defect_cell_1_21_2 1.68Birth defect_cell_1_21_3
GastroschisisBirth defect_cell_1_22_0 1 in 2,229Birth defect_cell_1_22_1 1871Birth defect_cell_1_22_2 4.49Birth defect_cell_1_22_3
OmphaloceleBirth defect_cell_1_23_0 1 in 5,386Birth defect_cell_1_23_1 775Birth defect_cell_1_23_2 1.86Birth defect_cell_1_23_3
Diaphragmatic herniaBirth defect_cell_1_24_0 1 in 3,836Birth defect_cell_1_24_1 1088Birth defect_cell_1_24_2 2.61Birth defect_cell_1_24_3
Chromosomal anomaliesBirth defect_cell_1_25_0
Trisomy 13Birth defect_cell_1_26_0 1 in 7,906Birth defect_cell_1_26_1 528Birth defect_cell_1_26_2 1.26Birth defect_cell_1_26_3
Trisomy 21 (Down syndrome)Birth defect_cell_1_27_0 1 in 691Birth defect_cell_1_27_1 6037Birth defect_cell_1_27_2 14.47Birth defect_cell_1_27_3
Trisomy 18Birth defect_cell_1_28_0 1 in 3,762Birth defect_cell_1_28_1 1109Birth defect_cell_1_28_2 2.66Birth defect_cell_1_28_3

See also Birth defect_section_24

Birth defect_unordered_list_4


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Birth defect.