Anti-D given during pregnancy at 28 and 34 weeks of pregnancy reduces the incidence of antibody formation and probably also reduces Rhesus alloimmunisation of women.
Women whose blood group is Rh-negative sometimes form Rh-antibodies when carrying a Rh-positive baby, in response to the baby's different red blood cell make-up. This sensitisation is more likely to happen during birth, but occasionally occurs in late pregnancy. These antibodies can cause anaemia, and sometimes death, for a Rh-positive baby in a subsequent pregnancy. Giving the mother anti-D after the first birth is known to reduce this problem. This review assessed two trials and found that giving anti-D during pregnancy is likely to help as well, although more research is required to confirm these possible benefits and identify any possible harms.