Inidcations for prenatal diagnosis in relatives of patients with neural tube defects.

We have reviewed the family histories of children with neural tube defects to determine which relatives are at sufficient risk to be offered amniocentesis for prenatal diagnosis. The recurrence risks for sibs was 6%; therefore, women with one affected child should be made aware of the availability of this test for monitoring subsequent pregnancies. The empiric recurrence risks for various groups of second and third degree relative exceeds 1% only for mothers' sisters' children. The lower values for the other groups may reflect either true biologic differences of reporting biases. Unit the matter is clarified, all sibs of affected children and all sibs of the parents of affected children should be informed of the availability of amniocentesis for monitoring their (or their spouse's) pregnancies.