Mifepristone: effect on plasma corticotropin-releasing hormone, adrenocorticotropic hormone, and cortisol in term pregnancy.

OBJECTIVE

To compare the effects of in vivo mifepristone with placebo on plasma corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and cortisol levels concentrations in term human pregnancies.

STUDY DESIGN

In all, 24 women participating in a randomized controlled trial of mifepristone for preinduction cervical ripening were enrolled in this ancillary study. Participants with uncomplicated singleton pregnancies beyond 41 weeks gestation and undilated, uneffaced cervices were randomized to either placebo or mifepristone 200 mg orally and observed for 24 hours prior to receiving either intravaginal misoprostol and/or intravenous oxytocin. Blood samples were obtained before medication administration, 3 and 6 hours later, and then every 6 hours until delivery. Plasma hormone levels were measured by radioimmunoassay.

RESULTS

Basal levels of CRH, ACTH, and cortisol were similar in the placebo (n=13) and mifepristone groups (n=11). Compared to placebo treatment, exposure to mifepristone resulted in significant elevation of plasma cortisol within 18 hours. Plasma CRH and ACTH were unaffected. Progression of labor was associated with significant increases in cortisol in both groups, while CRH and ACTH levels were not altered. Compared to basal levels within each group, plasma cortisol at delivery was significantly elevated within both the mifepristone (156.8+/-17.7 vs 332.6+/-48.5 ng/ml, p=0.008) and the placebo (166.6+/-34.3 vs 342.4+/-46.4 ng/ml, p=0.003) groups. However, plasma CRH, ACTH, and cortisol levels at delivery did not differ between the groups.

CONCLUSION

Mifepristone exposure and induced labor were associated with significant increases in plasma cortisol without alterations of systemic CRH or ACTH levels.