Prenatal genetic diagnosis in 350 amniocenteses.

Three hundred and fifty second trimester amniocenteses performed for prenatal diagnosis of genetic disorders are reported. One hundred and ninety-three of these were performed because maternal age was greater than 35 years, and 6 fetuses with unbalanced chromosomal abnormalities (3%) were identified. Thirteen procedures were performed because a previous child had had a neural tube defect; 1 anencephalic fetus was identified. Ninety-six percent of the initial taps were cultured successfully; we failed to obtain amniotic fluid in 3% of patients. The risk of a spontaneous abortion occurring at some time after the amniocentesis was 0.85%, and no cases of fetal injury were identified.