Antenatal prophylaxis of Rh immunization with 250 micrograms anti-D immunoglobulin.

Anti-D immunoglobulin (250 micrograms) was given i.m. to 830 Rh-negative primigravidae and multigravidae round the 32nd to 34th week of gestation. The multigravidae had previously been treated with anti-D immunoglobulin post partum or after abortion and had been followed up serologically after 8 months. Five hundred and twenty-nine of the women delivered Rh-positive infants and received another injection of anti-D immunoglobulin (250 micrograms) within 72 hours of delivery. At the serological follow-up 8 months after delivery 2 women (0.4%) had weak anti-D antibodies by the papain technique. No anti-D could be detected in these 2 women 14 and 20 months, respectively, after delivery. In a previously performed postnatal clinical study with 250 micrograms anti-D immunoglobulin the failure rate was 1.6% (10 out of 645 women). Thus, antenatal prophylaxis significantly (p less than 0.05) reduced the incidence of Rh immunization. The haemoglobin and bilirubin levels in cord blood and capillary blood did not differ in the Rh-positive and Rh-negative infants. Three primiparae (0.2%) had anti-D antibodies at the time of the antenatal injection before delivery. Thus, the antenatal regimen of gestation did not give full protection from Rh immunization. It is suggested that an antenatal injection at the 28th week of gestation would have been more effective, as Rh sensitization during pregnancy has been reported to be more frequent from the 29th week of pregnancy. Since the introduction of postnatal anti-D prophylaxis the Rh immunization occurring during pregnancy accounts for most of the observed failures (2, 4, 5, 14, 20). The efficacy and safety of antenatal injection of anti-D immunoglobulin has therefore been investigated (5, 6, 7). At the Växjö Hospital in Sweden, where the incidence of anti-D antibodies was 1.6% (15), 250 micrograms of anti-D immunoglobulin were given at about 32-34 weeks of gestation from March, 1973, to December, 1977. The results are presented here.