Abstract
Changes in the concentration of fetal hemoglobin in maternal blood during pregnancy and after delivery were studied in 91 pregnant women. Significant elevations of fetal hemoglobin were detected in the blood of ten women during the second trimester of pregnancy; these values fell toward normal during the ensuing pregnancy and post partum periods. In no instance could a rise in fetal hemoglobin be detected after delivery. The significance of these observations is discussed; it is suggested that acute hormonal changes early in pregnancy may be responsible for the reactivation of a fetal erythropoietic anlage with the resultant production by the mother of erythrocytes containing fetal hemoglobin. The method used was not sensitive enough, however, to detect minute amounts of fetal blood which may have crossed the placental barrier.
