I think you may be confusing the blood type with the Rh problem.
If an Rh negative mother has an Rh positive child (I think), the child may be born with a problem and need a replacement transfusion. Then again it may be the reverse. I know my mother was Rh negative and I am Rh positive, but I was the first. I think there are fewer problems if the mother waits 3 or more years between pregnancies.
you know I went back and looked into it, and we are both right, only I forgot (senior moment) to add RH into my argument.
Rh is the worse of the two it seems, although the jaundice caused by ABO incompatibility can lead to further complications if there’s no way to treat it.
I think both Rh and ABO compatibility would be important.
Thanks again for pointing out the RH factor too!
best regards, blu