FETAL RHESUS-D GENOTYPING ON AMNIOCYTES IN ALLOIMMUNIZED PREGNANCIES USING FLUORESCENCE DUPLEX POLYMERASE CHAIN-REACTION

Objective 1. To establish the reliability of fetal amniocyte Rhesus D (RhD) genotyping using fluorescence duplex polymerase chain reaction ( PCR) and 2, to assess the potential clinical impact on management of a lloimmunised pregnancies. Design Multicentre observational study. Sett ing Four departments of obstetrics and gynaecology in Germany. Methods Fourty-four amniotic fluid samples were obtained by amniocentesis fro m a retrospective group of 27 RhD alloimmunised pregnancies and 15 sam ples from 14 women treated prospectively. Two RhD gene specific fragme nts (exon 7 and 10) were amplified using two separate fluorescence dup lex PCR assays, and laser detected in an automated DNA sequence analys er. Results Amplification of the Rh gene sequences was successful in a ll samples. PCR at the two RhD gene regions resulted in complete conco rdance. Genotyping correctly predicted the RhD status of all fetuses s erotyped (n = 41). After intrauterine transfusions, PCR identified the RhD type of two fetuses more accurately than serotyping. Earlier know ledge of a negative RhD status would have rendered unneccessary 12 amn iocenteses in four fetuses of the retrospective study group, and preve nted further invasive testing in one fetus treated prospectively. In t he latter group, women with a positive fetal RhD genotype underwent in tensive prenatal care including serial invasive monitoring and intraut erine treatment. Conclusions Fetal RhD genotyping of amniocytes is a r eliable technique with the potential to improve routine management of alloimmunised pregnant women.