Circulating maternal corticotropin-releasing hormone and gonadotropin-releasing hormone in normal and abnormal pregnancies

Objective: Corticotropin-releasing hormone and gonadotropin-releasing hormone are produced by the human placenta and have been measured in the maternal circulation during pregnancy. Our objective was to determine concentrations of these substances in maternal plasma throughout normal pregnancies and in early pregnancy loss. Study Design: Fifty-one pregnant women were followed up prospectively and plasma samples were drawn at 8, 10, 12, 14, 16, 28, and 36 weeksʹ gestation and during labor. Specific and sensitive radioimmunoassays were used to determine corticotropin-releasing hormone and gonadotropin-releasing hormone concentrations in these samples. Results: Blood samples were drawn at all time points and outcome data were available from 33 women who completed their pregnancies at term without complications. In this normal group circulating corticotropin-releasing hormone concentrations increased from low or undetectable concentrations at 8 weeks (≤23.2±1.3 pg/ml, mean ±SEM) to measurable values at 16 weeks (34.3±2.2 pg/ml). Thereafter there was a significant increase to 1294±113 pg/ml in labor. Gonadotropin-releasing hormone demonstrated a trimodal distribution, increasing significantly from 8 to 14 weeks, decreasing at 16 weeks, and increasing again by term. The ratio of corticotropin-releasing hormone to gonadotropin-releasing hormone in the normal group demonstrated a 30-fold increase from 8 weeks to term. In eight cases of early pregnancy loss corticotropin-releasing hormone and gonadotropin-releasing hormone concentrations were not significantly different from those of the normal group in early pregnancy. In two cases of premature delivery gonadotropin-releasing hormone concentrations and ratios were within the normal range; corticotropin-releasing hormone levels were normal in both cases of premature delivery. Conclusion: In this study we determined maternal concentrations of corticotropin-releasing hormone and gonadotropin-releasing hormone in normal pregnancies and in labor at term. Neither maternal concentrations of corticotropin-releasing hormone nor gonadotropin-releasing hormone were useful in identifying pregnant women at risk for early pregnancy loss.