Red cell antibodies detected in antenatal tests on rhesus positive women in South and Mid Wales, 1948-1978.

A total of 733 rhesus positive women with antibodies were found during antenatal screening of 380,790 pregnancies in South and Mid Wales, over a 30-year-period. A steady increase was observed in the frequency of antibodies, particularly non-rhesus antibodies and the mothers concerned had a significantly increased history of previous blood transfusion. In 50 per cent of those with non-rhesus antibodies, transfusion was the only stimulus. Conversely, for the majority (61 per cent) of women with rhesus antibodies feto-maternal incompatibility was the sole apparent stimulus. No identifiable stimulus could be found in 25 per cent of women with anti-E and 13 per cent of those with anti-Kell. Compared to rhesus negative mothers with anti-D severe clinical haemolytic disease of the newborn was uncommon, but in 75 per cent of rhesus positive mothers with infants carrying the homologous antigen, there was some evidence of haemolytic disease. Anti-c was much the worst in this respect with 19.4 per cent of infants needing transfusion. The probability of having an incompatible infant was much less for the mothers with non-rhesus antibodies (27.3 per cent) and of these infants only 5.7 per cent needed transfusion.