What does a positive Coombs test indicate in an Rh-negative pregnant woman?

A positive Coombs test in an Rh-negative pregnant woman indicates that the mother has developed antibodies against Rh-positive red blood cells (RBCs). This typically occurs when an Rh-negative woman is exposed to Rh-positive blood, which may happen during pregnancy if the fetus inherits the Rh-positive factor from the father. The mother's immune system can respond by producing antibodies against the Rh antigen, which can cross the placenta and affect the fetus.

This test is crucial in monitoring potential Rh incompatibility issues such as hemolytic disease of the newborn, where the mother's antibodies attack the fetal RBCs, leading to anemia or other complications in the fetus. Detecting these antibodies early allows for appropriate management during the pregnancy and delivery to minimize risks for the baby.

The other options focus on scenarios that do not accurately reflect the implications of a positive Coombs test in this situation. The test specifically measures the mother's immune response rather than a lack of Rh factor or the fetal response regarding antibodies.