Genotipagem RHD fetal no plasma materno como ferramenta não invasiva na predição do risco da doença Hemolítica Perinatal em gestantes RHD negativo

Abstract

The management of RhD negative pregnant women is based on the premise that their fetuses may be at risk of developing hemolytic disease (DHPN), which could bring serious risks to the fetus. Invasive procedures such as amniocentesis or cordocentesis can be used to define the fetal RhD phenotype, however, it offers risks to both fetus and pregnant woman. The ability to detect fetal RHD gene in DNA from maternal plasma allowed a major advance in the care protocol to RhD negative pregnant women for being a non-invasive procedure and therefore carries no risk to the mother or fetus. Methods: 55 blood samples from RhD negative pregnants were processed for extraction of fetal DNA. Real time PCR was performed to amplify segments of exons 5 and 7 of RHD gene. The results of fetal genotyping using maternal plasma were compared with the RhD phenotype of newborns, performed in cord blood sample obtained at birth. PCR for detection of SRY gene and for the study of RHD zygosity was also performed, when the paternal sample was available. Results: The results of fetal RHD genotyping could be compared with 43 RhD phenotypes of newborn. There were five inconclusive results, no false negative and one false positive due to a probable incorrect RhD phenotyping. The test sensitivity was 100%, specificity was 94,1% and concordance between molecular and serological tests was 97,7% if we consider that the only discordant serological results was correct. However, in this case, genotyping from maternal plasma was concordant to that determined from the newborn buccal cells. Conclusion: The test for noninvasive fetal RHD genotyping was a sensitive and viable tool in management of RhD negative pregnants.