In utero diagnosis of congenital infections by direct fetal sampling.

Counseling for infections during pregnancy has traditionally focused on the clinical and laboratory findings of infection in the mother and the estimated risk of fetal damage associated with possible transmission of infection to the child. Now, with the use of techniques for fetal sampling, it is possible to diagnose infections of the fetus in utero and to correlate that information with the occurrence of fetal damage. The techniques that are available for sampling include amniocentesis, cordocentesis and chorionic villus sampling. The laboratory tests include: a) isolation of the organism in appropriate laboratory systems; b) detection of the DNA or RNA of the organism directly or with amplification with techniques such as PCR; c) detection of the organism by fluorescence or in situ hybridization; and d) identification of IgM or IgA fetal antibody to the organism by ELISA or similar methods. In utero infections can be documented for agents such as rubella, cytomegalovirus, parvovirus, Toxoplasma gondii and human immunodeficiency virus type 1. Further information is needed concerning the sensitivities and specificities of these methods for identifying fetal infection and predicting fetal damage.