Chronic alcohol abuse is associated with derangements of reproductive function in women. The mechanism of increased risk for alcohol-related abortions and fetal alcohol syndrome is unknown. The goal of this study was to determine if acute alcohol administration affected gonadal steroid hormone levels after administration of human chorionic gonadotropin (hCG) to normal healthy women. hCG was used to simulate the hormonal milieu during the first trimester of pregnancy. Ten women were studied during the mid-luteal phase (between days 17 and 23) of their menstrual cycle. Plasma estradiol, progesterone and prolactin were measured before and after simultaneous administration of 5000 I.U. of hCG (Profasi) and alcohol or placebo solution under double-blind conditions. There was a significant increase in plasma estradiol (P less than .001) and prolactin levels (P less than .01) after hCG and alcohol administration but not after hCG and placebo administration. Plasma progesterone increased significantly (P less than .001) above base line after hCG and placebo administration but this was not observed after hCG and alcohol administration. Since progesterone is essential for the maintenance of pregnancy, alcohol's attenuation of the expected progesterone response to hCG stimulation could increase the risk of spontaneous abortion. An alcohol-induced increase in estradiol after hCG administration could contribute to risk for fetal dysmorphology during the first trimester of pregnancy.