[Prenatal diagnosis]

A growing number of methods for the in-utero diagnosis of fetal disease became available during recent decades, mainly due to rapid advances in ultrasound technology and laboratory methods. Exclusion of fetal aneuploidy in pregnancies of women beyond 34 years is still by far the most common reason for an invasive procedure event at a time when the number of diagnosable inborn errors of metabolism and monogenetic disorders is increasing rapidly. Great efforts have been made to improve the poor predictive value of maternal age as an indicator for an increased risk for fetal aneuploidy. Maternal serum screening using various parameters [e.g. AFP, hCG, uE3] has been found effective in identifying the majority of pregnancies with Down syndrome in the second trimester. Current research goals are the optimal choice of markers and the introduction of maternal serum screening in the first trimester of pregnancy. Ultrasound is another suitable tool to identify pregnancies at high risk for aneuploidy at least in the hands of experienced operators. The diagnostic use of fetal cells in the maternal circulation is presently investigated in a large collaborative trial. Second trimester amniocentesis still is the most widely applied invasive technique in pregnancies with maternal age related risks for fetal aneuploidy. Safety and diagnostic accuracy are well established and amniotic fluid can easily be shipped. Without major changes in conventional sampling and laboratory techniques the procedure can be performed at 13 weeks of gestation and later. The safety and efficacy of first-trimester amniocentesis has still to be established in larger series. First-trimester chorionic villus sampling is a well-established alternative to amniocentesis with comparable procedure-related risks. It is the method of first choice in pregnancies at high risk for aneuploidy, inborn errors of metabolism and monogenic disorders, since uncultured villi can be used for a rapid diagnosis. Placental biopsy should also be considered in the second and third trimester of pregnancy for these indications whenever time is a critical issue. Fetal blood obtained by ultrasound-guided cordocentesis has successfully been used for the diagnosis of fetal infection and is at the same time another good source of cells for rapid karyotyping. Other invasive procedures such as fetal skin or liver biopsies for electron microscopy or specific metabolic tests are restricted to the relatively rare instances of diseases where DNA diagnosis is currently not available or uninformative. Providing information on the different alternatives in an individual situation is one of the critical issues in pregnancy care today.