neural tube defect

Any of a group of abnormalities caused by incomplete closure of the neural tube. These include: spina bifida, where part of the spinal cord and its membranes are exposed through a gap in the backbone; meningocele, where the meninges protrude through a gap in the spine; and anencephaly that is incompatible with life. These conditions can be detected by prenatal testing.

The incidence of NTDs varies throughout the world. In Britain and Ireland, which are among the worst affected countries, they represent the most serious central nervous system abnormalities seen at birth. A daily dose of folic acid, a vitamin in the B complex, for a month before conception and the first three months of pregnancy can reduce the risk of NTDs by around 75%. US research 1996 showed that obese women are twice as likely to have a baby with an NTD as women of normal weight.