The role of ultrasound in the early diagnosis of fetal structural defects following maternal anticonvulsant therapy.

A total of 162 pregnant subjects using anticonvulsant drugs were examined for fetal congenital defects over a period of five years. In 138 of these subjects, alpha-feto-protein (AFP) levels were determined in amniotic fluid at 16 weeks of gestation to rule out spina bifida. In all instances, a fetal anomaly scan was performed between 18 and 20 weeks of gestation. AFP levels were always within the normal range; neonatal examination revealed no spina bifida; however, in seven newborns, a single, or multiple structural defect was established. Apart from cases of severe hydrocephaly, hypospadia, and radius aplasia, the anomalies were too small to be detected by present-day ultrasound equipment. Couples should be informed of the limitations of ultrasound in the early detection of structural defects previously associated with the use of anticonvulsant drugs.