Anencephaly

Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development.[1] It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception.[2] Strictly speaking, the Greek term translates as "no in-head" (that is, totally lacking the inside part of the head, i.e. the brain), but it is accepted that children born with this disorder usually only lack a telencephalon,[3] the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually covered only by a thin layer of membrane—skin, bone, meninges, etc. are all lacking.[4] With very few exceptions,[5] infants with this disorder do not survive longer than a few hours or possibly days after their birth.

Anencephaly
Anencephalic baby.jpeg
An anencephalic baby
SpecialtyMedical genetics; pediatrics

Signs and symptoms

The National Institute of Neurological Disorders and Stroke (NINDS) describes the presentation of this condition as follows: "A baby born with anencephaly is usually blind, deaf, unaware of its surroundings and unable to feel pain. Although some individuals with anencephaly may be born with a main brain stem, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining awareness of their surroundings. Reflex actions such as breathing and responses to sound or touch may occur."[4]

Anencephaly-web
Illustration of an anencephalic fetus.
Anencephaly front
A front view of an anencephalic fetus
Babygram
X-ray of an anencephalic stillborn fetus

Causes

The cause of anencephaly is disputed by medical professionals and researchers.

Folic acid has been shown to be important in neural tube formation since at least 1991,[6][7] and as a subtype of neural tube defect, folic acid may play a role in anencephaly. Studies have shown that the addition of folic acid to the diet of women of child-bearing age may significantly reduce, although not eliminate, the incidence of neural tube defects. Therefore, it is recommended that all women of child-bearing age consume 0.4 mg of folic acid daily,[4] especially those attempting to conceive or who may possibly conceive, as this can reduce the risk to 0.03%.[8] It is not advisable to wait until pregnancy has begun, since, by the time a woman knows she is pregnant, the critical time for the formation of a neural tube defect has usually already passed. A physician may prescribe even higher dosages of folic acid (5 mg/day) for women having had a previous pregnancy with a neural tube defect.[8]

In general, neural tube defects do not follow direct patterns of heredity, though there is some indirect evidence of inheritance,[9] and recent animal models indicate a possible association with deficiencies of the transcription factor TEAD2.[10] Studies show that a woman who has had one child with a neural tube defect such as anencephaly has about a 3% risk of having another child with a neural tube defect,[11] as opposed to the background rate of 0.1% occurrence in the population at large.[12] Genetic counseling is usually offered to women at a higher risk of having a child with a neural tube defect to discuss available testing.

It is known that people taking certain anticonvulsants and people with insulin-dependent diabetes have a higher risk of having a child with a neural tube defect.[13]

Relation to genetic ciliopathy

Until recently, medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause despite the widely varying set of medical symptoms that are clinically visible in the disorders. Anencephaly is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and, thus, offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alström syndrome, Meckel-Gruber syndrome, and some forms of retinal degeneration.[14]

Diagnosis

Ultrasound Scan ND 066
Ultrasound image of fetus with anencephaly.

Anencephaly can often be diagnosed before birth through an ultrasound examination. The maternal serum alpha-fetoprotein (AFP screening)[15] and detailed fetal ultrasound[16] can be useful for screening for neural tube defects such as spina bifida or anencephaly.

Meroanencephaly

Meronanencephaly is a rare form of anencephaly characterized by malformed cranial bones, a median cranial defect, and a cranial protrusion called area cerebrovasculosa. Area cerebrovasculosa is a section of abnormal, spongy, vascular tissue admixed with glial tissue ranging from simply a membrane to a large mass of connective tissue, hemorrhagic vascular channels, glial nodules, and disorganized choroid plexuses.[17]

Holoanencephaly

The most common type of anencephaly, where the brain has entirely failed to form, except for the brain stem. Infants rarely survive more than one day after birth with holoanencephaly.[17]

Craniorachischisis

The most severe type of anencephaly where area cerebrovasculosa and area medullovasculosa fill both cranial defects and the spinal column. Craniorachischisis is characterized by anencephaly accompanied by bony defects in the spine and the exposure of neural tissue as the vault of the skull fails to form.[17][18] Craniorachischisis occurs in about 1 of every 1000 live births, but various physical and chemical tests can detect neural tube closure during early pregnancy.[19]

Prognosis

There is no cure or standard treatment for anencephaly and the prognosis for patients is death. Most anencephalic fetuses do not survive birth, accounting for 55% of non-aborted cases. Infants that are not stillborn will usually die within a few hours or days after birth from cardiorespiratory arrest.[4][20]

Four recorded cases of anencephalic children surviving for longer periods of time are Stephanie Keene (better known as Baby K) of Falls Church, Virginia, USA, who lived for 2 years 174 days; Vitoria de Cristo, born in Brazil in January 2010 and surviving until July 17, 2012;[21] Nickolas Coke[22] of Pueblo, Colorado, USA, who lived for 3 years and 11 months, and died October 31, 2012;[23][24] and Angela Morales, from Providence, Rhode Island,[25] who lived for 3 years and 9 months, and died December 16, 2017.[26]

In almost all cases, anencephalic infants are not aggressively resuscitated because there is no chance of the infants ever achieving a conscious existence. Instead, the usual clinical practice is to offer hydration, nutrition, and comfort measures and to "let nature take its course". Artificial ventilation, surgery (to fix any co-existing congenital defects), and drug therapy (such as antibiotics) are usually regarded as futile efforts. Some clinicians and medical ethicists view even the provision of nutrition and hydration as medically futile.

Epidemiology

In the United States, anencephaly occurs in about 1 out of every 10,000 births.[27] Rates may be higher among Africans with rates in Nigeria estimated at 3 per 10,000 in 1990 while rates in Ghana estimated at 8 per 10,000 in 1992.[28] Rates in China are estimated at 5 per 10,000.[28]

Research has suggested that, overall, female babies are more likely to be affected by the disorder.[29]

Ethical issues

Organ donation

One issue concerning anencephalic newborns is organ donation. Initial legal guidance came from the case of Baby Theresa in 1992, in which the boundaries of organ donation were tested for the first time.[30] Infant organs are scarce, and the high demand for pediatric organ transplants poses a major public health issue. In 1999, it was found that among children who die under the age of two, thirty to fifty percent do so while awaiting transplant.[30] In order for infant organs to be viable and used for transplant, they must be removed while the infant still has circulation or very soon after circulation has ceased. However, this poses both legal and ethical issues. In the United States, all states have laws that forbid the removal of organs from a donor until after the donor has died, except in the case of altruistic living donations of a kidney or liver segment.

The goal of those in support of organ donation is that it will further contribute to the pool of suitable organs for transplants while the need for lifesaving organ transplants is so great. It has been estimated that 400–500 infant hearts and kidneys and 500-1,000 infant livers are needed in the United States each year.[31] Because anencephalic neonates have partially functioning brain stems, they possess some brain stem reflexes such as spontaneous respirations. For this reason, these patients cannot be declared brain dead.

Within the medical community, the main ethical issues with organ donation are a misdiagnosis of anencephaly, the slippery slope argument, that anencephalic neonates would rarely be a source of organs, and that it would undermine confidence in organ transplantation.[32] Slippery slope concerns are a major issue in personhood debates, across the board. In regards to anencephaly, those who oppose organ donation argue that it could open the door for involuntary organ donors such as an elderly person with severe dementia. Another point of contention is the number of children who would actually benefit. There are discrepancies in statistics; however, it is known that most anencephalic children are stillborn.[32]

Proposals have been made to bypass the legal and ethical issues surrounding organ donation. These include waiting for death to occur before procuring organs, expanding the definition of death, creating a special legal category for anencephalic infants, and defining them as non-persons.[33]

In the United Kingdom, a child born with anencephaly was reported as the country's youngest organ donor. Teddy Houlston was diagnosed as anencephalic at 12 weeks of gestation. His parents, Jess Evans and Mike Houlston, decided against abortion and instead proposed organ donation. Teddy was born on 22 April 2014, in Cardiff, Wales, and lived for 100 minutes, after which his heart and kidneys were removed. His kidneys were later transplanted into an adult in Leeds. Teddy's twin, Noah, was born healthy.[34]

Brain death

There are four different concepts used to determine brain death: failure of heart, failure of lungs, whole brain death, and neocortical death.

Neocortical death, similar to a persistent vegetative state (PVS), involves loss of cognitive functioning of the brain. A proposal by law professor David Randolph Smith,[35] in an attempt to prove that neocortical death should legally be treated the same as brain death, involved PET scans to determine the similarities. However this proposal has been criticized on the basis that confirming neocortical death by PET scan may risk indeterminacy.[36]

Pregnancy termination

Anencephaly can be diagnosed before delivery with a high degree of accuracy. Although anencephaly is a fatal condition, the option of abortion is dependent on the abortion laws in the state.[31] According to a 2013 report, 26% of the world's population reside in a country where abortion is generally prohibited.[31] [37] In 2012, Brazil extended the right of abortion to mothers with anencephalic fetuses. This decision is, however, receiving much disapproval by several religious groups.[38]

Legal proceedings

The case of baby Theresa was the beginning of the ethical debate over anencephalic infant organ donation.[30] The story of baby Theresa remains a focus of basic moral philosophy. Baby Theresa was born with anencephaly in 1992. Her parents, knowing that their child was going to die, requested that her organs be given for transplantation. Although her physicians agreed, Florida law prohibited the infant's organs from being removed while she was still alive. By the time she died nine days after birth, her organs had deteriorated past the point of being viable.[39]

Baby K was an anencephalic infant that was kept alive for two years and 174 days under intensive care by order of the US Court of Appeals for the Fourth Circuit.

United States Uniform Acts

The Uniform Determination of Death Act (UDDA) is a model bill, adopted by many US states, stating that an individual who has sustained either 1) irreversible cessation of circulatory and respiratory functions or 2) irreversible cessation of all functions of the entire brain, including the brain stem, is dead. This bill was a result of much debate over the definition of death and is applicable to the debate over anencephaly. A related bill, the Uniform Anatomical Gift Act (UAGA), grants individuals and, after death, their family members the right to decide whether or not to donate organs. Because it is against the law for any person to pay money for an organ, the person in need of an organ transplant must rely on a volunteer.[31]

There have been two state bills that proposed to change current laws regarding death and organ donation. California Senate Bill 2018 proposed to amend the UDDA to define anencephalic infants as already dead, while New Jersey Assembly Bill 3367 proposed to allow anencephalic infants to be organ sources even if they are not dead.[31][40]

Research

Some genetic research has been conducted to determine the causes of anencephaly. It has been found that cartilage homeoprotein (CART1) is selectively expressed in chondrocytes (cartilage cells). The CART1 gene to chromosome 12q21.3–q22 has been mapped. Also, it has been found that mice homozygous for deficiency in the Cart1 gene manifested acrania and meroanencephaly, and prenatal treatment with folic acid will suppress acrania and meroanencephaly in the Cart1-deficient mutants.[41][42]

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External links

External resources
Abortion in Brazil

Abortion in Brazil is considered a crime against human life, being prohibited in all circumstances by articles 124-127 of the Penal Code. In 1940, however, Brazilian legislators withdrew the penalty of this crime when it is practiced if there is no other way to save mother's life or if the pregnancy is the result of a rape. This does not mean that the law regards abortion in these cases as a "right", but only that women who commit this crime will not be punished. The punishment for a woman who performs an abortion on herself or consents to an abortion performed by another outside these legal exceptions is one to three years of detention. The base penalty for a third party that performs an illegal abortion with the consent of the patient, ranges from one to four years of detention, with the possibility of increase by a third if the woman comes to any physical harm, and can be doubled if she dies. Criminal penalties fixed at four years or less can be converted to non-incarceration punishments, such as community service and compulsory donation to charity.Brazil is a signatory of the American Human Rights Convention, also called the Pact of San José. The Convention grants the right to life to human embryos, "in general, from the moment of conception", and has a legal status on a par with the Constitution in Brazilian Law. The Civil Code of Brazil also safeguards the rights of the unborn. In a 2008 case, however, the Supreme Federal Court ruled, by a 6-5 vote, that the right to life applies only to intrauterine embryos, and that frozen embryos not eligible to a uterus transfer do not hold fundamental rights and may be manipulated for research purposes. In 2012, the Supreme Court also authorized the practice of abortion on fetuses with anencephaly.

On November 29, 2016 the Supreme Court in Brazil ruled that "abortion should not be a crime when performed in the first three months of pregnancy". This ruling could potentially set a new precedent on law surrounding abortion in Brazil. It is very controversial, due to the fact that the Brazilian Government just passed a bill, earlier in 2016, which aimed to make Brazilian law on abortion even stricter.

Abortion in Iran

Abortion in Iran has been the subject of internal controversy for many years. Iran's abortion policy has been notoriously quick to change in accordance with changes in the regime; most significantly, the more modern policies developed by the government of Reza Shah under his family planning programs and moves towards more Western social policy were quickly deposed by Ayatollah Ruhollah Khomeini after he took power from the deposed shah in the Iranian Revolution of 1979.

Abortion was first legalized in 1978. In April 2005, the Iranian Parliament approved a new bill easing the conditions by also allowing abortion in certain cases when the fetus shows signs of handicap, and the Council of Guardians accepted the bill in 15/June/2005.

Abortion is currently legal in cases where the mother's life is in danger, and also in cases of fetal abnormalities that makes it not viable after birth (such as anencephaly) or produce difficulties for mother to take care of it after birth, such as major thalassemia or bilateral polycystic kidney disease. There is no need for a consent from the father and request and consent of mother with approval of three specialist physicians and final acceptance by legal medicine center suffices. Legal abortion is allowed only before 19th week of pregnancy.Much of the controversy has historically stemmed from Iran's status as a theocracy as it was established after the 1979 revolution; many policies, including those concerning social topics, are based on sharia law as interpreted from the Qur'an through the nation's Shi'a legal philosophy. While abortion is not actually referenced in the Qur'an, infanticide is specifically condemned, and this has been used as an argument to keep abortion illegal in most or all cases in which it might be sought. The sections of the Qur'an that detail the importance of health for women have been used to combat this argument, and have been moderately successful at changing the reactionary legislation against abortion enacted after 1979. Nowadays, most Islamic legal schools of thought hold that the ensoulment of a fetus takes place four months after conception, which has extended the discussion of abortion in many nations and communities that base their judicial codes off of Islamic law; in Iran, a consensus has recently developed that abortion is legitimate if it is before this four-month mark.Arguing for the legality or partial legality of abortion has the potential to be successful in Iran only if it is through religious discourse. All religious ruling in Iran has its final approval or veto assigned by the Guardian Council, a reviewing and regulatory body that has the ability to support or strike down all policies of Iran.

Acalvaria

Acalvaria is a rare malformation consisting of absence of the calvarial bones, dura mater and associated muscles in the presence of a normal skull base and normal facial bones. The central nervous system is usually unaffected. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. In other words, instead of having a skull cap protecting the brain, there is only skin covering it. The size of the area that is missing the skull cap can vary from case to case. In extreme cases, the entire top part of the cranium that is dome-shaped may be absent.

Acrania

Acrania is a rare congenital disorder that occurs in the human fetus in which the flat bones in the cranial vault are either completely or partially absent. The cerebral hemispheres develop completely but abnormally. The condition is frequently, though not always, associated with anencephaly. The fetus is said to suffer from acrania if it meets the following criteria: the fetus should have a perfectly normal facial bone, a normal cervical column but without the fetal skull and a volume of brain tissue equivalent to at least one third of the normal brain size.

Baby K

Stephanie Keene (October 13, 1992 – April 5, 1995), better known by the pseudonym Baby K, was an anencephalic baby who became the center of a major U.S. court case and a debate among bioethicists.

Birth defect

A birth defect, also known as a congenital disorder, is a condition present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth defects are divided into two main types: structural disorders in which there are problems with the shape of a body part and functional disorders in which there are problems with how a body part works. Functional disorders include metabolic and degenerative disorders. Some birth defects include both structural and functional disorders.Birth defects may result from genetic or chromosomal disorders, exposure to certain medications or chemicals, or certain infections during pregnancy. Risk factors include folate deficiency, drinking alcohol or smoking during pregnancy, poorly controlled diabetes, and a mother over the age of 35 years old. Many are believed to involve multiple factors. Birth defects may be visible at birth or diagnosed by screening tests. A number of defects can be detected before birth by different prenatal tests.Treatment varies depending on the defect in question. This may include therapy, medication, surgery, or assistive technology. Birth defects affected about 96 million people as of 2015. In the United States they occur in about 3% of newborns. They resulted in about 628,000 deaths in 2015 down from 751,000 in 1990. The types with the greatest numbers of deaths are congenital heart disease (303,000), followed by neural tube defects (65,000).

Cerebellar agenesis

Cerebellar agenesis is a rare condition in which a brain develops without the cerebellum. The cerebellum controls smooth movement, and when it does not develop, the rest of the brain must compensate, which it cannot do completely. The condition is not fatal on its own, but people born without a cerebellum experience severe developmental delays, language deficits, and neurological abnormalities. As children with cerebellar agenesis get older, their movements usually improve. It can co-exist with other severe malformations of the central nervous system, like anencephaly, holoprosencephaly, and microencephaly.The condition was first reported in 1831. 10 cases had been reported as of 1998. Agenesis of one half or another part of the cerebellum is more common than complete agenesis.Cerebellar agenesis can be caused by mutations in the PTF1A gene.

Cranioschisis

Cranioschisis (Greek: "κρανιον - kranion" skull, and "schisis - σχίσις" - split) is a developmental birth defect involving the skull. In this disease, the cranium fails to close completely (especially at the occipital region). Thus, the brain is exposed to the amnios, and eventually degenerates, causing anencephaly.

Exencephaly

Exencephaly, is a type of cephalic disorder wherein the brain is located outside of the skull. This condition is usually found in embryos as an early stage of anencephaly. As an exencephalic pregnancy progresses, the neural tissue gradually degenerates.

The prognosis for infants born with exencephaly is extremely poor. It is rare to find an infant born with exencephaly, as most cases that are not early stages of anencephaly are usually stillborn. Those infants who are born with the condition usually die within hours or minutes.

Gary Rohan

Gary Rohan (born 7 June 1991) is an Australian rules footballer who plays for the Geelong Football Club in the Australian Football League (AFL). Rohan is known for his pace and the ability to break lines with his dash out of defense. He started off his career playing at half-back but then soon moved forward because of his pace. Unfortunately he has had an injury-studded football career.

Iniencephaly

Iniencephaly, a term derived from the Greek word "inion" for nape of the neck, is a rare type of cephalic disorder that was first described by Étienne Geoffroy Saint-Hilaire in 1836. Those afflicted with the disorder all share 3 common characteristics: a defect to the occipital bone, spina bifida of the cervical vertebrae and retroflexion (backward bending) of the head on the cervical spine. Stillbirth is the most common outcome, with a few rare examples of live birth, after which death almost invariably occurs within a short time.

Lamina terminalis

The median portion of the wall of the forebrain consists of a thin lamina, the lamina terminalis, which stretches from the Interventricular foramen (Foramen of Monro) to the recess at the base of the optic stalk (optic nerve) and contains the vascular organ of the lamina terminalis, which regulates the osmotic concentration of the blood. The lamina terminalis is immediately anterior to the tuber cinereum; together they form the pituitary stalk.

The lamina terminalis can be opened via endoscopic neurosurgery in an attempt to create a path that cerebrospinal fluid can flow through when a person has hydrocephalus and when it is not possible to perform an Endoscopic third ventriculostomy, but the effectiveness of this technique is not certain.This is the rostral end (tip) of the neural tube (embryological central nervous system) in the early weeks of development. Failure of the lamina terminalis to close properly at this stage of development will result in anencephaly or meroencephaly.

List of fetal abnormalities

Fetal abnormalities are conditions that affect a fetus or embryo and may be fatal or cause disease after birth.

Acardiac twin

Achondrogenesis

Achondroplasia

Adrenal hematoma

Agenesis of the corpus callosum

Amniotic band syndrome

Anal atresia

Anencephaly

Aqueductal stenosis

Arachnoid cyst

Arthrogryposis

Camptomelic dysplasia

Cardiac rhabdomyoma

Caudal regression syndrome

Chorioangioma

Cleft palate

Club foot

Coarctation of the aorta

Conjoined twins

Cystic hygroma

Dandy-Walker malformation

Diaphragmatic hernia

Diastrophic dysplasia

Double outlet right ventricle

Duodenal atresia

Ebstein's anomaly

Ectopia cordis

Encephalocele

Endocardial cushion defect

Esophageal atresia

Exstrophy of the bladder

Fetal alcohol syndrome

Focal femoral hypoplasia

Gastrointestinal atresia

Gastroschisis

Holoprosencephaly

Hydranencephaly

Hydronephrosis

Hydrops fetalis

Hypoplastic left heart syndrome

Infantile polycystic kidney disease

Iniencephaly

Intracranial teratoma

Intrauterine growth retardation

Klippel-Trenaunay-Weber syndrome

Limb-body wall complex

Macrosomia

Meconium cyst

Meconium ileus

Microcephaly

Multicystic dysplastic kidney

Multiple pterygium syndrome

Oligohydramnios

Omphalocele

Osteogenesis imperfecta

Polydactyly

Polyhydramnios

Posterior urethral valves

Renal agenesis

Rh incompatibility

Sacrococcygeal teratoma

Spinal dysraphism

Syndactyly

Tetralogy of Fallot

Thanatophoric dwarfism

Transposition of the great vessels

Triploidy

Trisomy 13

Trisomy 18

Trisomy 21 (Down Syndrome)

Turner's syndrome (Monosomy X)

Twin-to-twin transfusion syndrome

Ureterocele

VACTERL association

Vein of Galen malformation

Ventricular septal defect

Miss D

Miss D refers to an abortion case in Ireland, Amy Dunne was a girl who wanted to travel to the United Kingdom for an abortion. Her identity was kept private at the time, and she was referred to only as D.

Miss D was a teenage girl who became pregnant while under HSE care in 2007. A scan of the foetus showed it suffering from anencephaly. This fatal foetal abnormality means the baby would not live for long outside the womb. D wanted to travel to the United Kingdom for an abortion, since abortion in Ireland was very heavily restricted. The HSE attempted to stop her going, from falsely telling her they had a court order preventing her from travelling, and would resort to physically restraining her if needed, and writing to the Garda Síochána asking them to stop her travelling. Since the Thirteenth Amendment of the Constitution of Ireland in 1992, it has not been illegal to travel outside Ireland for an abortion.

A High Court judge ruled that she had the right to travel to the UK, and strongly criticised the HSE's handling of the case. The HSE was ordered to pay costs, which were estimated at up to €1 million.She had a surgical, not medical abortion in the UK. The HSE refused to state if they paid for the abortion.

Mitzi's Abortion

Mitzi's Abortion is a play by a Seattle-based playwright, Elizabeth Heffron. The play dramatizes the journey of a young woman who is advised by her doctor to have a late-term abortion due to anencephaly, a severe birth defect, in her child. The social and cultural conflicts that arise as a result of her and her doctor's decision serve as the basis for the play. The play originally ran at the ACT Theatre in Seattle in the summer of 2006.

Neural tube defect

Neural tube defects (NTDs) are a group of birth defects in which an opening in the spinal cord or brain remains from early in human development. In the 3rd week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube. When the neural tube does not close completely, an NTD develops.

Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems.NTDs are one of the most common birth defects, affecting over 300,000 births each year worldwide. For example, spina bifida affects approximately 1,500 births annually in the USA, or about 3.5 in every 10,000 (0.035% of US births), which has decreased from around 5 per 10,000 (0.05% of US births) since folate fortification of grain products was started. The number of deaths in the US each year due to neural tube defects also declined from 1,200 before folate fortification was started to 840.

Polyhydramnios

Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in about 1% of pregnancies. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 24 cm.

There are two clinical varieties of polyhydramnios: chronic polyhydramnios where excess amniotic fluid accumulates gradually, and acute polyhydramnios where excess amniotic fluid collects rapidly.

The opposite to polyhydramnios is oligohydramnios, not enough amniotic fluid.

Prenatal testing

Prenatal testing consists of prenatal screening and prenatal diagnosis, which are aspects of prenatal care that focus on detecting problems with the pregnancy as early as possible. These may be anatomic and physiologic problems with the health of the zygote, embryo, or fetus, either before gestation even starts (as in preimplantation genetic diagnosis) or as early in gestation as practicable. Screening can detect problems such as neural tube defects, chromosome abnormalities, and gene mutations that would lead to genetic disorders and birth defects, such as spina bifida, cleft palate, Downs Syndrome, Tay–Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis, muscular dystrophy, and fragile X syndrome. Some tests are designed to discover problems which primarily affect the health of the mother, such as PAPP-A to detect pre-eclampsia or glucose tolerance tests to diagnose gestational diabetes. Screening can also detect anatomical defects such as hydrocephalus, anencephaly, heart defects, and amniotic band syndrome.

Prenatal screening focuses on finding problems among a large population with affordable and noninvasive methods. Prenatal diagnosis focuses on pursuing additional detailed information once a particular problem has been found, and can sometimes be more invasive. The most common screening procedures are routine ultrasounds, blood tests, and blood pressure measurement. Common diagnosis procedures include amniocentesis and chorionic villus sampling. In some cases, the tests are administered to determine if the fetus will be aborted, though physicians and patients also find it useful to diagnose high-risk pregnancies early so that delivery can be scheduled in a tertiary care hospital where the baby can receive appropriate care.

Rachischisis

Rachischisis (Greek: "rhachis - ῥάχις" - spine, and "schisis - σχίσις" - split) is a developmental birth defect involving the neural tube. This anomaly occurs in utero, when the posterior neuropore of the neural tube fails to close by the 27th intrauterine day. As a consequence the vertebrae overlying the open portion of the spinal cord do not fully form and remain unfused and open, leaving the spinal cord exposed. Patients with rachischisis have motor and sensory deficits, chronic infections, and disturbances in bladder function. This defect often occurs with anencephaly.

Craniorachischisis is a variant of rachischisis that occurs when the entire spinal cord and brain are exposed - simultaneous complete rachischisis and anencephaly. It is incompatible with life; affected pregnancies often end in miscarriage or stillbirth. Infants born alive with craniorachischisis die soon after birth.

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