BACKGROUND: The objective was the evaluation of the effect of the Dutch national routine antenatal RhIG (anti-D) immunization prevention (RAADP) program comprising one single dose of 200 μg (1000 IU) of RhIG in the 30th week of pregnancy, restricted to women without a living child.
STUDY DESIGN AND METHODS: A nationwide historic control study was performed. All newly detected anti-D–immunized para-1 in 1999, 2002, and 2004 were included and classified on the basis of received prophylaxis during the first pregnancy: antenatal and postnatal versus only postnatal RhIG. The numbers of D– parae-1 who delivered a D+ first child before the introduction (control group) or after the introduction (intervention group) of the RAADP were calculated from Vital Birth Statistics (8,700 and 12,000, respectively).
RESULTS: Fifty-eight newly detected anti-D immunizations in the first trimester were observed in the control group and 39 in the intervention group, which resulted in a significant reduction of the prevalence of new anti-D immunizations from 0.67 percent (95% confidence interval [CI], 0.50%-0.84%) to 0.31 percent (95% CI, 0.21%-0.41%). No reduction was observed in anti-D immunizations newly detected at the 30th-week screening (0.25%). A nonsignificant risk reduction of the risk of severe hemolytic disease of the fetus and newborn (HDFN) was found (0.23% vs. 0.10%). The numbers needed to treat to prevent one anti-D–immunized pregnancy and one case of subsequent severe HDFN were 357 and 1255, respectively.
CONCLUSIONS: RAADP of one single dose of 200 μg of RhIG in addition to postnatal RhIG (200 μg) halves the risk of anti-D immunization and subsequent severe HDFN.