What does it mean if I might have blood incompatibility with my baby?

Potential problem. Your body may react if exposed to your baby's blood. Such a reaction can affect red blood cells, white blood cells, or even platelets. Such reactions typically reduce the numbers of the affected cell type. The effects depend on the cell type affected and how much their numbers are reduced. Rhogam is given to rh-negative mothers during pregnancy and after birth to prevent a type of this problem.
Potential problem. If your blood type is "o" or if rh is negative and if the baby's blood type is "a" or "b" or rh positive, your baby may develop jaundice, anemia, heart failure or even too much accumulation of fluid in body parts (called as hydrops), especially with later pregnancy. All these can be managed by a maternal fetal medicine specialist or a high risk obstetrician. Some infants might just get jaundice.