Use of a single-exon method for fetal Rhesus (Rh) D screening early in pregnancy has been reported to be an appropriate option in the Western Swedish population, according to a study published recently in the journal Blood Transfusion.
This approach can be used to manage/prevent the occurrence of hemolytic disease of the fetus and newborn (HDFN), in which an RhD-negative pregnant woman carries an RhD-positive fetus.
It is well recognized that the Rh blood group is extremely complex, immunogenic, and polymorphic. In fact, the existence of RhD genetic variants in RhD-negative pregnant patients presents a challenge in fetal RhD genotyping. This is because these variants can potentially impact the antenatal management of anti-D prophylaxis.
Utilizing a 31-month follow-up, the researchers sought to establish the efficacy of a noninvasive single-exon technique in the obstetric population residing in Western Sweden. They evaluated the type and frequency of maternal RhD variants.
Further, researchers explored the association between maternal RhD variants and ethnicity and conducted assessments of inconsistent results between fetal RhD genotyping and serologic blood group was conducted.
Read more about HDFN symptoms and risks
Results of the study demonstrated that overall, 58.8% of the samples exhibited an RhD-positive fetal genotype, 38.0% of the samples had an RhD-negative fetal genotype, and inconclusive results were reported in 3.2% of the samples.
In a majority of these instances, the findings were observed among pregnant women of non-European ancestry. Strong positive reactions were seen in five samples obtained from pregnant women of European ancestry. Thus, in these cases, the blood group result was changed to RhD positive.
Of note, two novel alleles were recognized. There were seven cases with discordant results reported between fetal RhD genotyping and serology, which were shown to be associated with D antigen variants in newborns.
“The single-exon approach for fetal [RhD] screening early in pregnancy is an appropriate choice in the population of Western Sweden, with a very low frequency of inconclusive results caused by the presence of maternal [RhD] gene variants,” the authors emphasized. “Due to the high sensitivity, specificity, and accuracy of the test, [serologic] typing of neonates born to RhD[-]negative women has no longer been performed at our laboratory since June 2023,” they concluded.
