Introduction The relative importance of Kell antibody has increased since the reduction in Rhesus isoimmunisation. Although uncommon it is potentially a serious problem for the affected fetus because in addition to haemolysis it also causes bone marrow suppression. Women become sensitised through blood transfusions.

Aims There is little Irish data on Kell isoimmunisation and its effect on the fetus. We carried out this study in order to establish the frequency of the condition and the spectrum of severity in those affected.

Methods The records of the Blood transfusion department NMH were examined for the period 1984–2006 and those with anti-Kell antibodies identified.

Results During this period there were 176,000 births. There were 117 women who were anti-Kell antibody positive of which there were 16 affected fetuses (3 intrauterine deaths, 4 fetuses required intra-uterine transfusions, 1 required top-up transfusion after birth, 7 required phototherapy, 1 infant had long-term neurological sequelae).

Discussion This study gives an insight into the uncommon but important problem of Kell isoimmunisation. It is encountered in 1 in every 1,504 pregnancies. The data indicates that 13.6% of women with anti-Kell antibodies will have an affected fetus. In the 22 year epoch, sixteen affected fetuses were encountered. If this were extrapolated to the whole country we can expect 5.4 affected fetuses annually.

Conclusion This study highlights the problem of Kell isoimmunisation. As its relative importance has increased, those involved in perinatal medicine, both obstetrics and neonatology, need to have an understanding of its clinical significance and likely outcome.