Serum estradiol, estriol, progesterone, PRL, and hCG concentrations were measured at 4-week intervals in 40 pregnant women who chronically abused alcohol and in 20 abstinent pregnant women. Sixteen alcohol users gave birth to infants with the fetal alcohol syndrome (FAS), whereas the remaining 24 infants of alcohol users and all infants of the abstinent women were healthy. The women whose infants had the FAS had decreased estradiol and estriol levels throughout pregnancy. Progesterone levels also tended to be low. In contrast, the alcohol users had increased PRL levels during the 16-24th weeks of pregnancy compared with those in the abstinent women, but this rise was not related to the FAS. The concentrations of hCG fluctuated widely, without any consistent difference between alcohol users and abstinent women. Thus, heavy maternal abuse of alcohol resulting in FAS is accompanied, primarily or secondarily, by reduced estrogen concentrations throughout pregnancy and increased PRL levels during the 16-24th weeks of pregnancy.