Anencephaly

A lethal neural tube defect in which the cranial vault and most or all of the cerebral and cerebellar hemispheres fail to develop. It results from failure of the neural tube to close during the first month of embryogenesis — often before a woman knows she is pregnant. The risk of anencephaly and related defects such as spina bifida falls substantially when mothers have adequate folic acid around conception, through supplements or fortified foods. That evidence underpins mandatory folic acid fortification of flour in dozens of countries, one of public health nutrition’s clearest victories, and dietary guidance for women planning pregnancy.