A maternal warm-reactive autoantibody presenting as a positive direct antiglobulin test in a neonate.

Autoimmune hemolytic anemia in pregnancy is a rare cause of hemolytic disease of the newborn. This report describes a neonate with a mild hemolytic process and a positive direct antiglobulin test (DAT) presenting as the first manifestations of a maternal warm-reactive autoantibody. A full-term male neonate, blood group O, had a strongly positive DAT and laboratory evidence suggestive of a mild hemolytic process. The neonate's mother was also group O and had a negative antibody screen. Umbilical cord blood testing revealed a panreactive eluate though the antibody was not detected in cord serum. The neonate's mother was also found to have a positive DAT. A panagglutinin was identified in an eluate of her red cells, although the autoantibody could not be detected in her serum by a variety of sensitive techniques. There was no clinical or laboratory evidence of maternal hemolysis.