Evidence Library · Routine testing

Rhesus negative blood and the anti-D injection

Standard practice, on weaker trial evidence than most people assume.

If your blood is Rh negative and your baby's is Rh positive, your immune system can make antibodies that would attack a future baby's blood cells. Anti-D immune globulin, usually given at 28 weeks and after birth, is meant to prevent this.

The original Cochrane review reported that the risk of becoming sensitised during or after a first pregnancy is about 1.5%, and that anti-D at 28 and 34 weeks reduces it to about 0.2%.

The updated review, applying modern quality grading to the same two trials covering more than 4,500 women, found the effect on sensitisation was not statistically significant: relative risk 0.42 with a confidence interval of 0.15 to 1.17. It rated the evidence low quality.

Why this is hereAnti-D is almost certainly beneficial and is universally recommended. But the trial evidence is thinner than the confidence with which it is offered, and you are entitled to know that rather than being told it is proven.

Where this comes from:

164. McBain RD, Crowther CA, Middleton P. Anti-D administration in pregnancy for preventing Rhesus alloimmunisation. Cochrane Database Syst Rev. 2015;(9):CD000020.

165. Crowther CA, Keirse MJ. Anti-D administration in pregnancy for preventing rhesus alloimmunisation. Cochrane Database Syst Rev. 2000;(2):CD000020.

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