Lemire R J
Department of Pediatrics, University of Washington School of Medicine, Seattle.
JAMA. 1988;259(4):558-62.
Neural tube defects (NTDs) are a group of malformations of the brain and spinal cord that originate at various times during gestation. The most common NTDs are anencephaly and meningomyelocele, which arise during the process of neurulation, a well-defined period between the 17th and 30th day after ovulation. These NTDs are clinically apparent by being open, ie, leaving nervous tissue exposed, in contrast to postneurulation NTDs that are skin covered. The incidence of NTDs is declining in several areas of the world, including the United States. While the reasons for this are unclear, there seems to be some effect from prenatal diagnosis, genetic counseling, and possibly nutritional supplementation.
神经管缺陷（NTDs）是一组大脑和脊髓的畸形，在妊娠期间的不同时间出现。最常见的神经管缺陷是无脑儿和脊髓脊膜膨出，它们发生在神经胚形成过程中，即排卵后第17天至第30天这个明确的时期。这些神经管缺陷在临床上表现为开放性，即神经组织暴露在外，这与有皮肤覆盖的神经胚形成后神经管缺陷形成对比。神经管缺陷的发病率在世界上几个地区，包括美国，正在下降。虽然其原因尚不清楚，但产前诊断、遗传咨询以及可能的营养补充似乎起到了一定作用。
