I have a question from a clinician that I cant seem to answer despite checking ACOG guidelines:

Pt is Rh negative. Had amniocentesis five days ago, for which she received rhogam. Now she is scheduled for a D&C tomorrow (16 wks GA) and OB wants to know if more anti-D is indicated. 

I heard a rumor that there is an ACOG recommendation for these situations, but cant find it. My gut feeling is that to be safe, additional anti-D should be given, b/c the dose given for amniocentesis might not be large enough to cover for the D&C (ignoring the whole timing thing). Does anyone have any wisdom about this?

quick addendum - evidently we do not give microdoses, so she got a full dose for the amnio, which should cover the D&C!

If the pregnancy is more than 12 weeks I'd re-dose.   chances are it is overkill but I'd rather be safe too.

You could also do Kleihauer pre and post (I used to do that when we had an OB doing versions)

i ended up finding a reference that actually provided the half-life of rhogam, which is the product we use, and the minimum blood concentration needed to prevent immunization. it's the math behind the 28 week dose covering up to 40 weeks comes from,  i dont know why neither I nor my BB manager learned this during our training!

i also pinged a senior OB I trust about this stuff, and he said she's very likely covered by what she's already got, but can redose if so desired.

So since we gave her 300 mcgs a week ago, we advised that she is very likely completely covered (she should still have almost the full dose in her system just one week out), but that OB can dose again if she feels squirrely about it.

D. Salkin, thanks for your input! sounds about like what i ended up with.

 

I know you are in the USA, but you might find the BSH Guidelines on the subject useful.  Just put "BSH Guidelines" into your search engine, and go from there!

Malcom Needs, thank you, I will check it out!