Prognostic factors and management in pregnancies complicated with severe kell alloimmunization: experiences of the last 13 years.

Because of the recent referral of an anti-Kell sensitized pregnant woman, whose fetus became severely anemic despite intensive antepartum surveillance, the prevalence and characteristics of fetal Kell isoimmunization were reviewed and analyzed. Cases with Kell and RhD alloimmunization requiring intrauterine intravascular transfusions (IUT) at the Mount Sinai Medical Center during the 13-year period ending March 1998 were compared. Thirty-six fetuses with RhD and 5 with Kell isoimmunization required IUTs. Lower fetal and neonatal hematocrit levels were observed in the RhD group. A significantly higher incidence of polyhydramnios was found among fetuses with Kell isoimmunization and the maternal serum titers were much lower than those in the RhD group. DeltaOD450 values did not reliably reflect the Kell sensitized fetus's condition. There were no intrauterine deaths or neonatal direct hyperbilirubinemia in the Kell group, and the hemolytic disease of the newborn was more severe in the RhD group. Although the course of the hemolytic disease in our cases of Kell isoimmunization showed a better prognosis than that in the RhD group, the importance of this condition should not be underestimated, and differences in the pathophysiology of Kell and RhD alloimmunization should be taken into consideration during the management of these cases.