Kell alloimmunization in pregnancy: associated with fetal thrombocytopenia?
OBJECTIVE
Kell haemolytic disease in pregnancies has been suggested to be associated with decreased fetal platelet counts. The aim of this study was to evaluate the incidence and clinical significance of fetal thrombocytopenia in pregnancies complicated by Kell alloimmunization.


METHODS
In this retrospective cohort study, fetal platelet counts were performed in 42 pregnancies with severe Kell alloimmunization prior to the first intrauterine blood transfusion. Platelet counts from 318 first intrauterine transfusions in RhD alloimmunized pregnancies were used as controls.


RESULTS
Fetal thrombocytopenia (platelet count < 150 x 10(9)/l) was found in 4/42 (10%) in the Kell group and in 84/318 (26%) in the RhD group. None of the fetuses in the Kell alloimmunized pregnancies, including 15 with severe hydrops, had a clinically significant thrombocytopenia defined as a platelet count < 50 x 10(9)/l. In the RhD alloimmunized pregnancies, 2/230 (1%) of the non-hydropic fetuses and 7/30 (23%) of the severely hydropic fetuses had a clinically significant thrombocytopenia.


CONCLUSIONS
In contrast to fetuses with severe anaemia and hydrops due to RhD alloimmunization, fetuses with severe anaemia due to Kell alloimmunization are generally not at risk for substantial thrombocytopenia.
van den Akker
E S A
ES
Department of Obstetrics, Leiden University Medical Centre, Leiden, The Netherlands. e.s.a.van_den_akker@lumc.nl
Klumper
F J C M
FJ
Brand
A
A
Kanhai
H H H
HH
Oepkes
D
D
D001787:Blood Group Incompatibility; D015331:Cohort Studies; D004487:Edema; D005260:Female; D005333:Fetus / Q000276:immunology; D006801:Humans; D015994:Incidence; D007626:Kell Blood-Group System / Q000276:immunology*; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000276:immunology*; D011446:Prospective Studies; D012203:Rh Isoimmunization / Q000276:immunology; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000209:etiology* / Q000276:immunology
D007626:Kell Blood-Group System