Maternal Corticotropin-Releasing Hormone Is Increased with Impending Preterm Birth

The objective of this study was to test the hypothesis that maternal CRH concentrations are elevated in women experiencing threatened preterm labor who subsequently give birth within 24 h compared to those in women who do not. We also characterized the changes in maternal plasma cortisol, ACTH, corticosteroid binding capacity (CBC), and CRH concentrations in 28 healthy pregnant women between 20–38 weeks gestation. Overall, maternal plasma CRH concentrations were significantly greater (P < 0.05) in those women giving birth within 24 h (1343.3 ± 143.9 pg/mL; n = 81) compared to those in women who did not (714.5 ± 64.8 pg/mL; n = 144) or those in normal subjects. This difference was present between 28–36 weeks, but not 24–28 weeks gestation. The ratio of maternal cortisol to CBC was also significantly greater (P < 0.05; 0.65 ± 0.04; n = 82) in women giving birth within 24 h than in those who did not (0.55 ± 0.02; n = 136). This difference was significant at all gestational ages studied. Elevated CRH concentrations and bioavailability of free cortisol may both be implicated in the pathogenesis of preterm labor in some women. Further prospective clinical trials are warranted to determine the positive and negative predictive values of maternal CRH concentrations and/or the ratio of cortisol/CBC for identifying women with threatened preterm labor destined to give birth within 24 h.