The effect on the fetal pituitary-adrenal axis of dexamethasone administration early in the second trimester of pregnancy

Objective. To evaluate the effect of a single dose of dexamethasone to pregnant women at early second trimester on the fetal pituitary-adrenal axis. Methods. Thirty-eight women between 13 and 15 weeks' gestation were included in the study. Blood was taken from the mothers and their fetuses for the evaluation of plasma ACTH, cortisol, and free cortisol levels before and after treatment with a single dose of 1 mg of dexamethasone orally at 11 p. m. the night before the termination of pregnancy. Results. The mean plasma ACTH was significantly lower following dexamethasone administration (8.5 +/- 5.1 vs. 18.4 +/- 10.9 pg/ml). Similarly, plasma cortisol was significantly lower after dexamethasone treatment (208.3 +/- 168.7 vs. 772.7 +/- 206.1 nmol/l), as well as plasma free cortisol levels (2.6 +/- 0.0 vs. 6.1 +/- 6.1 nmol/l). Mean plasma ACTH levels were not significantly different in the fetuses after dexamethasone treatment (33.6 +/- 22.7 vs. 42.5 +/- 21.9 pg/ml). Moreover, mean fetal plasma cortisol was not different before and after treatment (108.2 +/- 27.2 vs. 94.3 +/- 47.2 nmol/l), as well as the mean free cortisol levels (7.7 +/- 5.2 vs. 7.0 +/- 4.3 nmol/l). Conclusions. A single dose of 1 mg of dexamethasone to the mother early in the second trimester of pregnancy does not result in a significant suppression of the fetal pituitary axis.