Can it be prevented? Yes. Measures of prevention are increasingly possible today. Pregnant women are tested routinely for the Rh factor and, if Rh negative, they can be immunized within 72 hours after the birth (or after the pregnancy terminates) and thereby prevent adverse consequences of blood incompatibility in subsequent pregnancy. If the woman has not been immunized, the consequences of blood incompatibility in the newborn can be prevented by exchange transfusion in the baby. If a newborn baby has jaundice, this can be treated by phototherapy in the hospital nursery. Other preventive programs are directed toward reducing exposure of pregnant women to virus and other infections; unnecessary exposure to X-rays, drugs and medications; and the control of diabetes, anemia and other nutritional deficiencies. Of great importance are optimal well-being prior to conception, adequate prenatal care, and protecting children from accidents or injury.