Management of pregnancies complicated by anti-kell isoimmunization

Objective: To assess the efficacy of managing pregnancies complicated by an ti-Kell isoimmunization using the methods developed for evaluating anti-Rh- D isoimmunization. Methods: We reviewed 156 anti-Kell-positive pregnancies seen from 1959 to 1 995, which were managed with serial maternal titers, amniotic fluid Delta O D450 determination, and funipuncture. Data on maternal titers, paternal phe notypes, invasive fetal testing and therapies, and neonatal outcomes were c ollected and analyzed to determine whether severely affected pregnancies we re identified in time for successful fetal and neonatal therapy. Results: Twenty-one fetuses were affected, eight with severe disease, and t wo fetuses in this group died. All of the severely affected fetuses were as sociated with maternal serum titers of at least 1:32. A critical titer of 1 :32 was found to be 100% sensitive for identifying the affected pregnancies . The affected group had significantly higher amniotic fluid Delta OD450 va lues over the range of gestational ages than did the unaffected group (P <. 001). The upper Liley curve was a specific discriminator for the diagnosis of affected fetuses, and the lower curve was specific for the diagnosis of unaffected or mild cases. Conclusion: Fetal anemia due to anti-Kell isoimmunization might be dde in p art to erythropoietic suppression, but it is still largely a hemolytic proc ess. The methods based on a hemolytic process, including use of a critical maternal serum titer of 1:32, serial amniotic fluid analyses when the titer was exceeded, and liberal use of funipuncture, were successful in identify ing severely affected fetuses. (C) 1999 by The American College of Obstetri cians and Gynecologists.