Fetal sex and prenatal betamethasone therapy.

We examined the influence of fetal sex on the occurrence of respiratory distress syndrome in premature infants after maternal treatment with betamethasone. Among treated infants of 1,251 to 1,750 gm birth weight, the incidence of RDS was 40.9% in 22 males and 7.1% (P = 0.03) in 14 females. Cord serum levels of betamethasone were similar for infants of both sexes, and there was no sex difference in suppression of serum cortisol, dehydroepiandrosterone sulfate, and growth hormone after treatment. These findings suggest that prenatal corticosteroid therapy is less effective in male infants than in female infants. This effect is not due to a difference in transfer or metabolism of betamethasone, nor is it reflected in the responsiveness of the fetal hypothalamic-pituitary-adrenal axis to synthetic glucocorticoid.