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

A positive Coombs test in an Rh-negative woman indicates that the mother has autoantibodies against Rh-positive red blood cells (RBCs). This test is performed to detect antibodies that are potentially harmful to the red blood cells of a fetus, particularly in cases where the mother is Rh-negative and the father is Rh-positive.

In normal circumstances, an Rh-negative mother who has not been sensitized (exposed to Rh-positive blood) would not have these antibodies. A positive result suggests that there has been some form of sensitization, which could result from a previous pregnancy with an Rh-positive fetus, a blood transfusion, or other scenarios where Rh-positive blood cells may have entered the mother's circulation.

Understanding the implications of a positive result is crucial, as the presence of these autoantibodies can endanger a fetus with Rh-positive blood. This situation can lead to hemolytic disease of the newborn, where the mother's antibodies attack the fetal red blood cells, leading to anemia, jaundice, and potentially more severe complications.

The other options do not accurately represent the clinical significance of a positive Coombs test in this context.