Plasma immunoreactive erythropoietin in normal women studied sequentially during and after pregnancy.

Six healthy, nonanemic women with uncomplicated singleton pregnancies were sequentially studied for plasma immunoreactive erythropoietin levels, hematologic indices, and human placental lactogen. Mean group levels of erythropoietin as well as human placental lactogen were significantly increased (p less than 0.01) after 18 weeks' gestation compared to nonpregnant values (20 to 30 weeks post partum). However, individual responses of erythropoietin during pregnancy were found to be highly variable. There was a direct correlation of both maternal plasma erythropoietin and human placental lactogen with gestational age (p less than 0.001) but no detectable relation of erythropoietin with human placental lactogen levels. We speculate that the increase in erythropoietin levels during pregnancy acts as a trophic stimulus for effecting an increase in maternal red blood cell mass presumably to meet the increased metabolic (oxygen) demands of pregnancy.