Serum unconjugated estriol levels during spontaneous labor.

We measured maternal serum unconjugated estriol (SUE3) levels in 244 cases (218 cases with labor and 26 without labor) and investigated the relationships among several obstetrical factors and SUE3 levels. There was no significant difference in the SUE3 level between the group with labor and the group without labor. However, the SUE3 level decreased gradually with prolonged duration of labor in multipara. There were significant positive correlations between the SUE3 levels and birth weights (n = 82, r = 0.375, p less than 0.01) or placental weights (n = 82, r = 0.381, p less than 0.01) in the multipara with labor. The SUE3 levels of fetal distress cases (n = 30, 20.0 +/- 8.6 ng/ml) were significantly (p less than 0.05) lower than those without fetal distress (n = 188, 24.5 +/- 9.7 ng/ml). These data suggest that maternal SUE3 might have been affected with feto-placental function, even after the onset of labor SUE3 levels decrease with prolonged duration of labor.