Simultaneous and serial measurement of serum levels of human placental lactogen, beta-human chorionic gonadotropin and unconjugated estriol levels in pregnant women.

Serum levels of human placental lactogen (hPL), beta-human chorionic gonadotropin (beta-hCG) and unconjugated estriol (E3) were measured simultaneously and serially in regular menstrual late pregnant women (155 samples) by radioimmunoassay. The peak of beta-hCG level was shown at 37 weeks' gestation. After that, there was a moderate decline of the beta-hCG level. Serum hPL showed the peak at 30 weeks' gestation. The level of unconjugated E3 rose toward 41 weeks' gestation. In the 155 samples, there were significant positive correlations among these hormone levels. Also, there were highly significant positive correlations between placental weight and these three hormone levels. Only unconjugated E3 level which was obtained within a week before the onset of labor had a significant positive correlation with birth weight. These data suggest that even in late pregnancy, maternal beta-hCG makes a peak and may change parallel with hPL and unconjugated E3. Only the unconjugated E3 level may be affected by fetal growth.