To ask whether blood groups can change?

[Lmmontgomery]

When my son was born we were told he was A negative. He's now 20 and has just found out he's A positive.

Is it possible that his blood group has changed and he's developed the rhesus protein after not being born with it, or must the hospital have made a mistake?

I work in a hospital blood transfusion lab. As previous posters have mentioned, it is possible to change blood group if you’ve had a bone marrow/stem cell transplant. It’s possible for your recorded group to change over time due to inprovements in techniques for picking up weaker D-types. It is also perfectly possible that mistakes could have been made in manually transcribing baby groups years ago that are not possible now due to automation and computer interfacing that take potential human error out of the equation. When I started my training we did all grouping using test tubes, coloured solutions and hand-wrote all results. Now analysers do all the measuring out and use bead columns and cameras, feeding back to the computer to report groups.
Very occasionally a baby may be reported as having the same group as mum if the midwife sampling the cord hasn’t quite got the right part and actually sent us mum’s blood and not baby’s. We have an additional test to check this (foetal cells react differently from adult ones), and it would be picked up, but this may not have been routine years ago, either. This was why I was recorded as A RhD negative (my mum’s group) until I became a donor and found out that I’m actually A RhD positive.
Sorry for the ramble. Hope it helped.

Oh heck I didnt think you could change.

I refused the anti D as both husband and I were negative. They wanted to give me anti D under not being sure the husband was def the father but I told them he 100% was and they said if I was sure it was him (!) I wouldnt need it!

Sorry, I flouted MN convention then, didn’t I?
My post should have started with “Biomedical Scientist here: ask me anything!”

Thanks igglepiggle for correcting altiara - My blood type for surgery, childbirth etc is recorded as O neg not because it's the universal donor but because that's the only type of blood I can receive. I have partial D blood so am neither negative nor positive and my blood group is O.