Screening for neural tube defects.

Neural tube defects are separated into two main categories: (1) abnormalities of the skull and brain (anencephaly, acrania, and encephalocele) and (2) malformations of the spine (meningomyelocele or spina bifida). The cause of neural tube defects is not always clear, and include chromosomal abnormalities, single gene mutations, maternal disease, or maternal exposure to teratogens. Mostly the disorder emerges as a multifactorial trait. Routine screening for neural tube defects was introduced in the United Kingdom in the mid-1970s and the United States in the mid-1980s. The use of screening has resulted in a marked decline in the frequency of neural tube defects diagnosed at birth.