Fetal leucocyte count in rhesus disease

The effect of fetal anaemia on the total and differential leucocyte counts was studied by examining blood samples obtained by cordocentesis from 177 previously untransfused rhesus affected fetuses at 17-36 weeks' gestation. The mean fetal total leucocyte, lymphocyte, and monocyte counts were significantly lower than the corresponding values in normal controls and there were significant associations between the decrease in these cells and the degree of fetal anaemia. Possible mechanisms for leucopenia include (i) stimulation of erythroid progenitor production at the expense of production of myeloid progenitors, (ii) non-specific haemophagocytosis, or (iii) general suppression of haemopoiesis. Further understanding of the underlying mechanism and the implications of leucopenia as well as the previously reported thrombocytopenia and anaemia may provide a basis for improved antenatal and/or postnatal treatment.