[Present situation of prenatal diagnosis of neural tube defects].

Anencephaly and spina bifida both are malformations of unknown etiology which are caused by an absent or incomplete closure of the neural tube. The risk of recurrence for the malformations is 5% in families with one child with a neural tube defect and 10%, if two such children have already been born. Neural tube defects can be diagnosed already before 20th week of gestation by ultrasonics and alpha-fetoprotein measurement in amniotic fluid, if an underdeveloped neurocranium or a free communication between amniotic and cerebrospinal fluid is present. By these diagnostic techniques and possibly following interruption the probability in risk families can be significantly lowered.