Is there a need to administer a further dose of Rh (D) immunoglobulin if a delivery is delayed beyond 40 weeks’ gestation?
It is a common and widespread practice to offer induction of labour to women who have reached 10 days beyond their due date and now there are very few pregnancies which progress beyond 42 weeks. In clinical trials, the estimated half-life of Rh (D) Immunoglobulin has been shown to be approximately 4 weeks and it is generally accepted that a dose of 625 IU (125 mcg) of Rh (D) immunoglobulin provides coverage for a period of 6 weeks. If the half-life is approximately 4 weeks, the difference in antibody level in an uncomplicated pregnancy 6 weeks after the injection as compared to 8 weeks is unlikely to be significant. It would be expected that any significant FMH event occurring after term would be likely to precipitate labour or lead to medical intervention to deliver the baby and this would then be followed shortly after by the administration of the postnatal dose of Rh (D) immunoglobulin. Therefore, for an uncomplicated pregnancy that proceeds up to 42 weeks, there is no need to give
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