Any science types that can answer my question?

[MayimBialik]

I'm rhesus negative and having my routine anti-D injection today. Went to the hospital a couple of days ago for bloods to be done.

However, I have had anti-D a couple of times already in this pregnancy due to bleeds and last time the Kleihauer test showed up positive for antibodies but the lab had put a note saying that it would have been because of a previous dose of anti-D in my system.

My bloods I had done the other day will also show up as this as I last had to have an injection about 2 weeks ago for a bleed. So my question is, how can they tell whether a rhesus neg woman has made antibodies/become sensitised? Would they only know for sure at the beginning of my next pregnancy when they do the bloods at my booking and my body is clear of any anti-D? Or can they differentiate between anti-D and antibodies?

Hope that makes sense!

You won't become sensitised to positive blood. The anti d just reduces your bodies reaction to it, hence having top up jabs and the need in future pregnancies.

Just as someone who has an organ transplant remains on anti rejection drugs for life, while ever you are pregnant it is safer to have the anti d.

I see what you mean. I think they can probably tell the difference. I don't know this for sure but am assuming so, otherwise why bother doing the Kleihauer test at any time after anti D has been given since it would always give a "false positive"?

Also, when I was tested for toxoplasmosis, I was told they would be able to tell the difference between recent infection and immunity from an old infection - i.e. new antibodies vs old antibodies - so something similar may be the case with differentiating between anti D vs sensitisation antibodies.

Are you worried that you may have had a sensitising event but not had a jab?

No I'm pretty sure I won't have developed antibodies, but I suppose you never know.

After having anti-D today my notes say that the blood test showed that I was positive for antibodies but that this is likely to be because of previous anti-D injections. The midwife confirmed that they wouldn't be able to tell me if I had made antibodies until the booking in bloods of my second pregnancy.

So be warned if you have had to have anti-D before the routine injection as looks like they can't differentiate between the 'false' antibodies and any real ones.