One single dose of 200 microg of antenatal RhIG halves the risk of anti-D immunization and hemolytic disease of the fetus and newborn in the next pregnancy.

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 microg (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 microg of RhIG in addition to postnatal RhIG (200 microg) halves the risk of anti-D immunization and subsequent severe HDFN.