Obstetric history and antibody titer in estimating severity of Kell alloimmunization in pregnancy

To evaluate the usefulness of the obstetric history and the maternal serum Kell antibody titer in the management of pregnancies with Kell alloimmunization.

In a retrospective cohort study of 41 pregnancies complicated by Kell alloimmunization, the obstetric history, divided into presence or absence of a previous Kell-positive child, and Kell antibody titers in the index pregnancy were correlated with the gestational age at the onset of fetal anemia.

Women with a previous Kell-positive child had a lower gestational age at the first intrauterine transfusion compared with those without a previous Kell-positive child (P=.01). However, in two of 29 pregnancies in the latter group, severe fetal anemia requiring transfusion was detected before 20 weeks of gestation. In neither group were maternal Kell antibody titers significantly correlated with gestational age at first intrauterine transfusion (P=.62 and P=.72, respectively). In all but two pregnancies (1:2 and 1:4, respectively), antibody titers were at least 1:32 before the first intrauterine transfusion.

For timely detection of all cases of severe fetal anemia, Kell-alloimmunized pregnancies with a Kell-positive fetus and titers greater than or equal to 1:2 should be closely monitored from 16 to 17 weeks of gestation onward.