Midtrimester amniocentesis for prenatal diagnosis. Safety and accuracy.

This prospective study of the safety and accuracy of midtrimester amniocentesis involved 1,040 subjects and 992 controls. Immediate complications of amniocentesis (vaginal bleeding or amniotic fluid leakage) occurred in approximately 2% of the women. There was no statistically significant difference between the two groups in rate of fetal loss (3.5% for the subjects, 3.2% for the controls) or incidence of complications of pregnancy of delivery. Newborn examination indicated no significant differences between the two groups in incidence of congenital anomalies and no evidence of physical injury resulting from amniocentesis. The two groups did not differ significantly in physical, neurological, or developmental status at one year of age. Diagnostic accuracy was 99.4%. Midtrimester amniocentesis is a highly accurate and safe procedure that does not significantly increase the risk of fetal loss or injury.