RESEARCH – December 2005

Non-invasive prenatal diagnosis of fetal rhesus D status by analysis of maternal plasma


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Objective. Feto-maternal rhesus D (RhD) incompatibility is a serious and potentially life-threatening condition for the growing fetus. Correct determination of the fetal RhD status is useful in the treatment of sensitised RhD-negative pregnant women. Traditionally, determination of the fetal rhesus D status has been accomplished by invasive prenatal diagnosis (amniocentesis and chorionic villus sampling). Recently, non-invasive prenatal diagnosis, established by using fetal DNA isolated from maternal peripheral blood, became available for antenatal determination of the fetal RHD genotype.

The aim of the current study was to develop a non-invasive prenatal diagnosis method for fetal RhD typing using fetal DNA separated from maternal plasma.

Methods. Peripheral blood samples were obtained from 36 pregnant women during the second and the third trimesters of pregnancy. DNA was extracted from maternal plasma and fetal RHD genotyping was performed in parallel using conventional PCR and real-time PCR (Q-PCR). The results of RHD genotyping were retrospectively compared with newborn’s serology tests to determine the accuracy of the applied methods.

Results. Fetal RHD genotyping was performed for 36 RhD-negative women being pregnant with 21 RhD-positive and 15 RhD-negative fetuses. The fetal RhD status was correctly determined in 91,7% (33/36) and 94,4% (34/36) of pregnancies using PCR and Q-PCR techniques, respectively. The sensitivity and specificity for the conventional PCR analysis of fetuses of the RhD-negative pregnant women were 95.2% and 86.7%, and for Q-PCR analysis were 95.2% and 93.3%, respectively. The analysis of our results did not reveal any statistical differences between the outcomes of the fetal RhD determinations using either PCR or Q-PCR methods.

Conclusions. The results of the current study demonstrate that non-invasive fetal RHD genotyping can be performed rapidly and reliably with the use of fetal DNA obtained from maternal plasma. The high level of accuracy of this technique would allow to suggest it for use on a routine basis for the management of pregnant RhD-negative patients.