<unk> s <unk> s) are a group of birth<unk> s in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the<unk> <unk> . When the<unk> <unk>  does not close completely, an<unk>  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.<unk> s are one of the most common birth<unk> s, affecting over 300,000 births each year worldwide. For example, spina bifida affects approximately 1,500 births annually in the United States, 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<unk> s also declined from 1,200 before folate fortification was started to 840.
Neural tube defect
Birth defect
Congenital limb deformities
Craniofacial abnormality
Vocal cord dysfunction
Neonatal sepsis
Perinatal asphyxia
Renal hypoplasia