The normal values of red cell counts and indices, white cell counts, platelet counts and activities of haemostatic mechanisms vary with age, sex and pregnancy state.^[1,2] There are also genetic and common environmental factors which can affect the reference ranges in certain populations.^[3] It is especially important that the difference in reference ranges in all stages of life be appreciated by health workers in tropical countries, where up to half the population are aged under 15 years and women experience numerous and often complicated pregnancies.