Elevated umbilical cord plasma erythropoietin levels in prolonged pregnancies

Objective: To determine if umbilical cord plasma erythropoietin levels are elevated in pregnancies that continue beyond their expected date for delivery. Methods: Erythropoietin was measured using an enzyme-linked immunosorbent assay in 124 appropriately grown newborns delivered from 37-43 weeks' gestation. Each woman had an uncomplicated labor and delivery course without evidence of fetal stress or meconium. The comparison was made between pregnancies ending at 37-40 weeks' gestation and those at 41-43 weeks' gestation. Results: There was no difference between the two groups in cord blood gases or Apgar scores at 1 and 5 minutes. Cord plasma erythropoietin levels were significantly higher in pregnancies delivered after 41 completed weeks' gestation (41 or more weeks: 48.0 +/- 7.1 mIU/mL, n = 45 versus 37-40 weeks: 26.1 +/- 4.2 mIU/mL, n = 79, P < .001). When compared with pregnancies delivered between 37 and 40 weeks, erythropoietin levels were significantly elevated in pregnancies delivered at either 41, 45 or 43 weeks' gestation. Conclusion: In pregnancies reaching 41 weeks and beyond, cord plasma erythropoietin levels are significantly increased, indicating altered fetal oxygenation in some of these pregnancies. These results support the current practice of close fetal surveillance of prolonged pregnancies. (C) 1998 by The American College of Obstetricians and Gynecologists.