Anencephaly is the result of the neural tube in an embryo not closing all the way, according to the Centers for Disease Control and Prevention. The neural tube in the embryo eventually develops into the spinal cord and the brain, according to Genetics Home Reference.
Because the neural tube does not close the way it should, the cells that form the brain and the spinal cord are bathed in amniotic fluid and degenerate, explains Genetics Home Reference. As a result, anencephalic babies are born without the front parts of their brain, the cerebellum and cerebrum. These parts of the brain are responsible for coordination, vision, hearing, emotion and thinking.
Anencephaly is incurable and untreatable, and nearly all anencephalic babies die shortly after birth, reports the CDC. The babies of Hispanic mothers are at greater risk for anencephaly than other ethnic groups, but as of 2015, researchers have been unable to determine why.
Medical experts are also unclear on exactly what causes anencephaly, adds the CDC. Doctors recommend that a woman who wants to get pregnant start taking folic acid supplements even before she conceives. Folic acid is known to reduce the risk of neural tube defects. Women trying to become pregnant should also avoid cigarettes and alcohol.