Screening for irregular maternal blood group antibodies and fetal blood group determination

Abstract

Alloimmunization due to blood group incompatibility, especially in the rhesus gene, is a rare but usually severe complication in pregnancy, which can lead to intrauterine fetal death when untreated. Therefore, a blood group determination and antibody screening should already be performed in the first trimester. The aim of this screening test is to detect high-risk pregnancies due to irregular maternal antibodies at an early stage. The introduction of standardized prepartum and postpartum anti‑D immunoprophylaxis in rhesus (Rh) D negative pregnant women has significantly reduced RhD alloimmunization. Nowadays, noninvasive testing of cell-free fetal DNA in maternal blood also offers the possibility to determine fetal Rh antigens prepartum. This opens up the possibility to identify the population at risk and selectively provide targeted anti‑D immunoprophylaxis. In the case of positive detection of fetal RhD in RhD negative pregnant women, anti‑D immunoglobulin is usually administered at 28–30 weeks of gestation. If alloimmunization has nevertheless occurred with an increased risk of fetal anemia, referral to a perinatal center or fetomaternal specialist is indicated. If fetal anemia is suspected a fetal blood transfusion via umbilical cord puncture can be lifesaving.