Increased Immunoreactive Erythropoietin in Cord Plasma and Neonatal Bilirubin Production in Normal Term Infants After Labor

The purpose of this investigation was to compare immunoreactive erythropoietin levels in umbilical cord plasma and neonatal bilirubin production in infants born of normal women who delivered with or without labor. Two groups of term (38 to 42 weeks) singleton pregnancies were compared1) those delivered by repeat elective cesarean section without prior labor (N = 17), and 2) those delivered vaginally or by cesarean section after labor (N = 24). None of the infants was asphyxiated, and there was no difference in Apgar scores between the no-labor and labor groups. The cord plasma erythropoietin levels were lower in the infants of women who had repeat elective cesarean section without labor than in those whose mothers had labor before delivery (Wilcoxon rank sum test, P < .025). The median erythropoietin for the no-labor group was 22.9 mU/mL compared with 38.8 mU/mL for the labor group. The pulmonary excretion rate of carbon monoxide (Veco), an index of bilirubin production, for the no-labor group was 14.3 ± 6.2 SD μL/kg per hour compared with 18.0 ± 4.9 SD μL/kg per hour for the labor group (P < .05). The hemoglobin concentration for the no-labor group was 16.0 ± 1.5 SD g/dL compared with 17.7 ± 2.2 SD g/dL for the labor group (P < .05). The Veco correlated with the hemoglobin concentration (N = 32, r = 0.37, P < .05). The results of the present study suggest that labor is normally associated with increases in the cord plasma erythropoietin level. This is consistent with relatively greater in utero hypoxemia than that observed in the absence of labor.