Noninvasive screening for prenatal genetic diagnosis.

During the last two decades a number of methods of prenatal diagnosis have become available and have been used either in laboratory research or in routine genetic counselling. Despite the effectiveness of invasive sampling procedures in diagnosing genetic disorders, their use involves some risk. The advantage of noninvasive methods is that they provide an opportunity to make a genetic diagnosis without risk, and therefore are applicable for use in mass screening programmes. This article reviews three different approaches to noninvasive prenatal genetic diagnosis and offers conclusions and recommendations for their use. Maternal serum screening is a well-understood technique that should be universally offered to pregnant women, regardless of their risk status. Invasive tests can be used, as indicated, once serum testing results have been obtained. Although ultrasonography cannot be recommended for routine use, it can provide a useful adjunct to serum screening and deserves further investigation. Elaboration of fetal cells from maternal blood is a promising technique but can only be considered investigational on the basis of current research, and should not serve as the sole basis of clinical decision-making.