An obstetrical patient has had 3 previous pregnancies. Her first baby was healthy, the second was jaundiced at birth and required an exchange transfusion, while the third was stillborn. Which of the following is the most likely cause?

The situation described suggests a pattern indicative of Rh incompatibility, which is characterized by the mother's blood type being Rh-negative and the fetus's blood type being Rh-positive. In the case of the obstetrical patient, the sequence of pregnancies is significant. The first child, being healthy, may have either been Rh-negative like the mother or simply not affected. The second child experienced jaundice and required an exchange transfusion, a common treatment for hemolytic disease of the newborn (HDN) caused by Rh incompatibility, indicating that the mother developed antibodies against Rh-positive blood, leading to the destruction of fetal red blood cells. The third child being stillborn aligns with more severe cases of Rh disease, which can result in fetal demise in utero when not properly managed.

ABO incompatibility typically causes milder hemolytic reactions and is less likely to result in severe outcomes such as stillbirth or the need for exchange transfusion. Immune deficiency disease does not specifically correlate with the pattern of the past pregnancies outlined. Congenital spherocytic anemia is a hereditary condition that would not fit the scenario of recurring pregnancy complications as described. Thus, this patient's history points convincingly towards Rh incompatibility as the underlying cause for the outcomes seen