Antenatal glucocorticoid administration increases corticotrophin-releasing hormone in maternal plasma.

OBJECTIVE

This study was designed to determine whether maternal corticotrophin-releasing hormone (CRH) concentrations are altered after maternal betamethasone administration for fetal lung maturity in women with threatened preterm labour and whether these effects are dependent on gestational age.

METHODS

Our study included 49 women with threatened preterm labour who received prenatal betamethasone for fetal lung maturity between 24 and 31 weeks of gestational age and 11 women who did not. Maternal blood was taken before and after glucocorticoid administration or at 24 hours after initial sampling. Plasma CRH, adrenocorticotrophin (ACTH) and cortisol concentrations were determined by radioimmunoassays. The women were stratified into 24-25 weeks, 26-27 weeks, 28-29 weeks, and 30-31 weeks completed gestation.

RESULTS

At each gestational age, maternal cortisol concentrations decreased by approximately 85% after glucocorticoid administration. Overall mean cortisol values fell from 580.0 (SD, 351.8) to 89.7 (96.6) nmol/L (n = 40, P < 0.001). Overall mean ACTH values decreased from 9.9 (4.7) to 5.0 (3.4) pmol/L (n = 43, P < 0.001), and the approximate 50% decrease was similar at each gestational age. In marked contrast, overall mean CRH values increased from 58.0 (37.0) to 87.8 (68.6) pmol/L (n = 49, P < 0.001) after betamethasone administration. There was no change in maternal cortisol, ACTH or CRH values over 24 hours in women who did not receive betamethasone.

CONCLUSIONS

We conclude that maternal betamethasone administration increases maternal plasma CRH values between 24 and 31 completed weeks of gestation.