Medical Q&As

Anti-D - top up needed?

I am 21 weeks pregnant and Rhesus negative. I experienced some bleeding during the first 3 months of pregnancy but this has now stopped. At that time I was given an anti-D injection. I recently had a nasty fall; do I need to have a top-up anti d injection? I did not hurt my abdomen, nor have I experienced any pains or bleeding.

All of the remarks I am about relate to Rhesus negative mothers only. A standard dose of anti-D is given following a sensitisation event that occurs within the first twenty weeks of pregnancy. The term sensitisation event refers to situations where the motherís immune system is exposed to the blood of the foetus. For example, abdominal injury, vaginal bleeding or threatened miscarriage could result in some leakage of foetal blood into the maternal circulation. This would then result in the formation of antibodies against the blood of the foetus. The anti-D injection was given to you at 3 months to prevent such a reaction taking place. That one injection should be sufficient to protect you from being sensitised to the Rhesus factor. The second accident did not involve any trauma to your abdomen therefore a second injection would not be indicated since that accident would not qualify as a sensitisation event.