text: if a woman blood is a+ and a man blood is ab+, does this has an effect on the new born bady?   it will determine what types of blood types the baby may have.  but, apparently there can't be any adverse affects.  if a father's rh factor genes are + +, and the mother's are + +, the baby will have one + from the father and one + gene from the mother. the baby will be + + rh positive. (this is the case for a+ and ab+ parents)  problems with the rh factor occur when the mother's rh factor is negative and the baby's is positive. sometimes, an incompatibility may occur when the mother is blood type o and the baby is either a or b.  see the source for further information, or ask your doctor because i'm not in the medical profession.