Q: I am a 27 years old female with B negative blood group. I have been asked to go for anti-D injection in the eight month of pregnancy. As far as I have heard, this injection is given during the second pregnancy and only if the first baby’s and the mother’s blood groups are opposite. Should I get myself injected with anti-D vaccine?

A:The development of anti-D antibodies generally results from fetomaternal haemorrhages (baby's blood getting in the mother) occurring in RhD negative women who carry RhD positive fetus. The most important cause of anti-D antibodies is immunisation during pregnancy. Late immunisation during a first pregnancy can occur in up to 25% of cases. Therefore, it is advisable to take the anti D injection even if you are pregnant for the first time. Two doses of anti-D immunoglobulin of 500 IU (one at 28 weeks and one at 34 weeks) should be given. In your situation, I would suggest you take one dose now - as you have gone past the 28 week period. Following delivery take at least 500 IU of anti-D Ig within 72 hours following the delivery if the baby is RhD positive. There is no universal policy regarding the postnatal dose as it varies in different countries. To see if the dose is enough you may have a blood test as soon as possible (within two hours) after delivery to undertake a test called Kleihauer screening test to identify if you need additional anti-D injection. Additional dose is usually advised if the fetomaternal hemorrhage is greater than 4 ml.