Pregnancy risks
This has nothing to do with your “letter” blood type, or the type determined by the ABO grouping system. This has to do with the Rh factor, which determines whether your blood type is positive or negative.
This factor could cause complications in pregnant women if the baby’s Rh blood type is different from the mother’s. For instance, if the mother has a negative blood type and the baby has a positive one, the mother’s body can actually build up antibodies against the baby’s blood type.
Luckily, this doesn’t affect the baby, but it could have a disastrous effect on future pregnancies. Fortunately, doctors can give pregnant women a shot early in their pregnancy that can prevent Rh-incompatibility problems.
