ERYTHROPOIETIN IN HUMAN FETUSES WITH IMMUNE HEMOLYTIC-ANEMIA AND HYDROPS-FETALIS

Objective: To determine whether plasma erythropoietin is increased in fetuses with anemia due to Rh isoimmunization. Methods: Hemoglobin and erythropoietin were measured in samples obtained by funipuncture from 15 fetuses with Rh isoimmunization (gestational age 26.2 +/- 5.0 week s, mean +/- standard deviation) and from 13 control fetuses (23.1 +/- 6.7 weeks). Hemoglobin and erythropoietin also were determined in umbi lical cord blood collected at birth from 20 term fetuses delivered by elective cesarean. Results: Fetuses with Rh isoimmunization had lower hemoglobin and higher plasma erythropoietin measurements than mid-gest ation controls (6.1 +/- 3.9 versus 10.7 +/- 1.5 g/dL and 105.5 +/- 168 .1 versus 12.5 +/- 3.1 mU/mL, P < .05, respectively). Hemoglobin and p lasma erythropoietin increased with gestational age in control fetuses . There was an inverse association between hemoglobin and plasma eryth ropoietin in control and Rh-isoimmunized fetuses (r = -0.56, P < .005) . Using multiple linear regression, hemoglobin and gestational age wer e associated independently with plasma erythropoietin (overall F2,25 = 12.3, multiple r2 = 0.49, P < .001). Despite marked decreases in hemo globin, fetuses below 24 weeks' gestation had minimal increases in pla sma erythropoietin compared to fetuses above that gestational age. Mil dly anemic Rh-isoimmunized fetuses (hemoglobin 11.6 +/- 2.0 g/dL) deli vered vaginally had significantly higher erythropoietin levels in umbi lical cord plasma than Rh-isoimmunized fetuses with comparable hemoglo bin (10.9 +/- 3.5 g/dL) delivered by elective cesarean without labor ( 1246 +/- 856 versus 106 +/- 66 mU/mL, respectively, P < .05). Conclusi on: Fetuses with anemia at mid to late gestation respond with increase s in plasma erythropoietin, but these changes are substantially attenu ated before 24 weeks' gestation.