New cases of irregular blood group antibodies other than anti-D in pregnancy. Frequency and clinical significance.

The frequency of irregular blood group antibodies detected for the first time in pregnant women during the period 1975-80 has been examined. Whereas Rh(D)-negative gravidae in Norway are examined immuno-hematologically three times during pregnancy, Rh(D)-positive women are tested once only, usually early in pregnancy. Nevertheless, about one-third of the new cases of immunization within the Rh system were found in the Rh-positive women. In the latter, anti-E and anti-c were the Rh antibodies most frequently encountered. Among other irregular antibodies which can cause hemolytic disease of the newborn (HDN), those of the Kell and Duffy systems are the ones second in frequency and clinical significance to the Rh antibodies. In the present series about 40% of the new cases of immunization within the Rh, Kell and Duffy systems were found in Rh-positive women. This proportion would undoubtedly have been greater if also the Rh-positive women had been retested for the presence of irregular blood group antibodies towards the end of the gestation. Such a retesting of Rh-positive gravidae is desirable both for a better prediction and early diagnosis of HDN and to facilitate the procurement of compatible blood if the woman should need an emergency blood transfusion.