Background

The discovery of cell-free fetal DNA (cfDNA) in maternal plasma has led to the development of non-invasive methods to determine the fetal RHD genotype. This enables targeted antenatal anti-D prophylaxis only to woman with presumably RhD positive babies and is introduced in Slovenia from 2018 (1). After almost five years of introduction we were interesting in advantiges and disadvantages of targeted antenatal prophylaxis in our region of northeastern Slovenia.

Methods

Between 2018 and 2023, we received 2216 samples of pregnant women in 25- 26 weeks' of gestation. Fetal RHD genotype was determined in Blood Transfusion Center Ljubljana with real time PCR using the GenAmp PCR System 9700. The presence of intron 5, exon 7 and 10 on the RHD gene and SRY gene are assesed. After genotyping RhD we phenotyped only samples of cord blood presumably RhD positive newborns. We looked retrospectively at the results, medical documentation and analyzed how many pregnant women were treated according to the accepted principles of targeted protection, how many really needed protection and how many units of IgG anti-D were saved.

Results

From 1 October 2018 to 30 April 2023, we received 2216 samples of RhD negative pregnant women. According to the RHD genotyping, 1297 (58 %) fetuses were RhD-positive, so we advised protection with anti-D immunoglobulin at 28 weeks of pregnancy, and 901 (41 %) fetuses were RhD-negative, so pregnant women did not need protection. In 18 (1 %) cases, the predicted RhD phenotype of the fetus was inconclusive, therefore we advised protection with anti-D imunoglobulin as recommended. With the introduction of the national programme pregnant women receive imunoglobulin anti-D targeted protection according to the predicted foetal RhD phenotype. During the mentioned period, the use of anti-D immunoglobulin was reduced by at least 901 units.

Conclusion

With the introduction of targeted antenatal anti-D prophylaxis we confirmed that predicted phenotype of the fetuses in 41% of RhD-negative pregnant women is negative. Side effects of the drug are avoided in these pregnant women. The rational use of anti-D immunoglobulin is important due to the limited source of obtaining, as the immunization of male voluntary donors is ethically controversial in many countries.

Offenlegung Interessenkonflikt:

T Dovč Drnovšek, et all. Reliable Determination of Fetal RhD Status by RHD Genotyping from Maternal Plasma. Transfus Med Hemother. 2013 Feb; 40(1): 37–43.

Invited talks abstract/summary