Major reduction in occurrence of anti‐c and anti‐E in pregnancy after more than 10 years of preventive matched transfusion with most benefit for c‐matching

Summary Extension with cE‐matching of the transfusion policy for women under 45 years to prevent alloimmunization and hemolytic disease of the foetus and newborn (HDFN) was evaluated. After implementation of cEK‐matching, anti‐c occurrence decreased from 46.8 to 30.4 per 100 000 pregnancies (RR 0.65, 95% CI 0.54–0.79), while anti‐E occurrence decreased from 122.1 to 89.9 per 100 000 pregnancies (RR 0.74, 95% CI 0.66–0.84). The c‐negative women showed a higher anti‐E occurrence before cEK‐matching and a more pronounced decline with the new policy. This indicates that cEK‐matched transfusion effectively reduces alloimmunization, and that a cK‐matched approach could prevent most transfusion‐related alloimmunization and HDFN.