Erythropoietin (EPO) levels were measured using an ELISA method in umbilical cord plasma from 68 appropriately grown neonates at 27 to 43 weeks of gestation (EGA). A consistent but small (5%) difference was found between the EPO levels in the umbilical artery (Ua), 21.0 +/- 2.5 mlU/mL (mean +/- SEM), and umbilical vein (Uv), 22.0 +/- 2.7 mlU/mL (p<0.02, n=30). Significant inverse correlations were found between Ua EPO levels and pO(2) (r=-0.44, p<0.002), pH (r=-0.68, p<0.0001), as well as base deficit (r=-0.56, p<0.0001). A significant correlation was found between ECA and Ua EPO from 27 to 43 weeks of gestation (r=0.45, p<0.001, n= 68). One and 5 minute Apgar scores did not correlate with EPO. These findings indicate that EPO correlates strongly with cord gas parameters and thus ma): serve as a clinically useful marker for both subacute fetal distress and chronic uteroplacental insufficiency.