The physiology of maternal and fetal erythropoiesis in pregnancy shows that hematopoiesis, and the stimulation of hematopoiesis, take place separately in the two circulations. Erythropoietin appears the main regulator in both mother and fetus. The human placenta forms a manifest barrier to endogenous and recombinant erythropoietin, thus fulfilling the cardinal precondition for the use of recombinant erythropoietin in the treatment of maternal pregnancy anemia. The prevalence of maternal anemia in pregnancy and post partum is high; up to 95% of cases are due to iron deficiency, compounded post partum by blood loss during and after delivery. Use of rHuEPO for reversing pregnancy and postpartum anemia has given promising initial results.