Changes in placental lactogen, beta 1-chorionic gonadotropin, and unconjugated and total estriol levels in the late course of normal human pregnancy.

The levels of human placental lactogen (hPL), beta-human chorionic gonadotropin (beta-hCG), unconjugated estriol (UE3) and total estriol (TE3) were measured radioimmunologically in women along their course of pregnancy. The serum hPL and beta-hCG levels were relatively constant in uncomplicated pregnancy, while UE3 and TE3 significantly rose towards 41 weeks of gestation. There were positive correlations between hPL and beta-hCG (n = 49, r = 0.737, p less than 0.001), and between UE3 and TE3 (n = 49, r = 0.904, p less than 0.0001). The ratios of placental hormones to estriol showed moderate declines towards 41 weeks of gestation. These data suggest that the fetal adrenal function increased toward the term, while the placental peptide hormones decrease or remain unchanged. Determination of serum unconjugated estriol was found to be convenient and useful for monitoring the fetoplacental function.