The Yorkshire antenatal anti-D immunoglobulin trial in primigravidae.

2069 Rh(D)-negative women in their first pregnancy received 100 micrograms doses of anti-D immunoglobulin at 28 and 34 weeks' gestation and a further dose at delivery if the infant was Rh(D)-positive. The antibody status was determined at 28 weeks, 34 weeks, at delivery, and 6 months after delivery. The findings were compared with those in a control group of 2000 Rh(D)-negative primigravidae who gave birth to Rh(D)-positive infants and received the standard post-delivery injection of anti-D immunoglobulin. 2 women in the trial group and 18 in the control group became actively immunised during the first pregnancy. 325 women in the trial group have had a further Rh(D)-positive pregnancy and in 2 anti-D antibodies were detected for the first time. 528 control women have had a further Rh(D)-positive pregnancy and anti-D was demonstrable in 29-18 in whom antibodies developed during the first pregnancy and 11 in whom antibodies first appeared during the second. The reduction in the incidence of sensitisation was significant. It is estimated that the extra cost in anti-D immunoglobulin was approximately pounds 1600 for each woman sensitised.