Comparison of pregnancy outcome after amniocentesis for previous neural tube defect or raised maternal serum alphafetoprotein.

Amniocentesis was performed in 219 pregnancies because a previous pregnancy produced a fetus with neural tube defect (NTD) and in 212 pregnancies in which the indication for amniocentesis was a high maternal serum alphafetoprotein (AFP) level. The proportion of abnormal fetuses, the frequency of low birth weight infants, and the frequency of undesired fetal loss were significantly greater in the group with high maternal serum AFP, in which there was also a significant excess of male births. It is concluded that maternal serum AFP screening defines a group of high risk pregnancies. The greater fetal loss and low birth weight associated with high maternal serum AFP levels were not the result of amniocentesis but were an inherent feature of these pregnancies.