Alcohol, smoking, and incidence of spontaneous abortions in the first and second trimester.

32,019 women completed a questionnaire on alcohol use at their first antenatal visit; thereafter they were followed to assess the incidence of spontaneous abortions. 51.7% reported drinking no alcohol in early pregnancy; 44.7% had less than 1 drink daily; and 2.4, 0.4, and 0.1% had an average of 1-2, 3-5, or more than 6 drinks respectively. Life-table analysis showed that the age-adjusted relative risks of second-trimester losses (15-27 weeks) were 1.03 (not significant: ns), 1.98 (p < .01), and 3.53 (p < .01) for women taking less than 1, 1-2, and more than 3 drinks daily, compared with non-drinkers. The corresponding relative risks for first-trimester losses (5-14 weeks) were 1.12 (ns), 1.15(ns), and 1.15(ns). Smokers had relative risks of 1.01(ns) and 1.21(ns) in the first and second trimesters, compared with non-smokers. The increased risk of second-trimester miscarriage in drinkers was not explained by age, parity, race, marital status, smoking, or the number of previous spontaneous or induced abortions. Thus alcohol may harm human fetuses not only when it is abused but also when taken in moderation.