ABO incompatibility

Definition:

ABO incompatibility can result when the fetal blood type differs from the mother's blood type.

Causes, incidence, and risk factors:

A, B and O are the major blood types. ABO incompatibility between the mother and fetus can occur if:

• the mother is O and the fetus is B or A or AB. (most common- represents almost 100 percent of the cases)
• the mother is A and the fetus is B or AB (extremely uncommon)
• the mother is B and the fetus is A or AB (extremely uncommon)

In these cases, the mother creates antibodies against the fetus' incompatible blood type. These antibodies cross the placenta into the fetus' blood stream where they begin to destroy the fetus' blood cells.

ABO incompatibility is similar to Rh incompatibility but generally creates much milder problems than Rh incompatibility. Newborn infants affected by ABO incompatibility may have elevated levels of bilirubin and become jaundiced (whites of the eyes and skin become yellow). Severe ABO incompatibility problems may require an exchange transfusion. However, most ABO incompatibility is relatively minor and the jaundice it produces can usually be treated with bili-lights (phototherapy).