Developments in laboratory techniques for prenatal diagnosis.

Ongoing trends in prenatal diagnosis aim at early, rapid, and ideally noninvasive diagnosis as well as at the improvement of risk-screening for aneuploidy. Interphase-fluorescence in situ hybridization and quantitative fluorescence polymerase chain reaction are efficient tools for the rapid exclusion of selected aneuploidies in addition to the established direct preparation of chromosomes from chorionic villi. Interphase fluorescence in situ hybridization has also made possible the diagnosis of selected chromosome abnormalities in single cells (e.g. in preimplantation genetic diagnosis) or noninvasive diagnosis. More complex multicolor fluorescence in situ hybridization approaches are currently being evaluated. Single cell polymerase chain reaction is the key technique for the molecular diagnosis of a growing number of monogenic conditions before implantation or, still more experimental, in fetal cells retrieved from the maternal circulation. New sources for noninvasive diagnosis came into play such as fetal DNA or cell nuclei in maternal plasma. The combination of biochemical parameters in the maternal serum, namely free beta-human chorionic gonadotropin with pregnancy associated plasma protein A and sonographic markers, has already dramatically increased the sensitivity of risk screening in the first trimester of pregnancy.