What is the combination of blood types that affects fetus?

ABORh types.: Incompatibility of the rhesus system (usually antigen d) when the mother is negative and the fetus positive can result in fetal anemia from destruction of red cells as a result of maternal antibodies crossing the placenta. A milder form of anemia occurs at birth when the mother and fetus are discordant for ABO blood group - this rarely causes problems in utero but may cause mild anemia in nursery.

See below: Usually this is seen with a type o mother and a type a or b child.