Evaluation of a new Swedish protocol for alloimmunization screening during pregnancy

Screening protocols for alloimmunization during pregnancy usually make a difference between primi- and multigravidae as well as between Rh(D) negative and Rh(D) positive pregnant women. We have evaluated a new screening program including antibody tests at 25 and 35 gestational weeks only, for all, and regardless of Rh(D) group. During the time period 1983-89, 78,300 consecutive pregnancies were tested. Red cell antibody immunizations were detected in 287 (0.37%) pregnancies subdivided into fourteen different red cell IgG antibody specificities. Significant antibody titers (defined as IAT or enzyme titers ≤8) were observed in 225 pregnancies, where 127 (56%) were previously unknown. A majority (63%) of the new immunizations occurred among the Rh(D) positive pregnant women. All newborns that needed phototherapy or exchange transfusion due to alloimmunization were recognized at the time of delivery. We conclude that antibody screening tests at 25 and 35 gestational weeks for both Rh(D) negative and positive pregnant women is sufficient, effective and a safe procedure for the fetus as well as for the mother.