How common is having blood incompatibility during birth?

Not uncommon: Blood incompatibility between mom and baby may lead to increased levels of jaundice during the newborn period. Incompatibility is due to antibodies within the mother's blood, which may be secondary to a mismatch between blood types (mom is type o and the baby is a or b, or mom is rh- and baby is rh+), or the presence of an unusual antibody, which is typically screened for during pregnancy.

Rarely problematic: Many mothers with babies with rh incompatibility get rhogam, a medication which decreases its severity of the incompatibilty many other types of blood incompatibility may require special light therapy (phototherapy). Nowadays, babies very rarely need special type of blood transfusion, known as exchange transfusion.