Patterns of alcohol consumption during pregnancy.

Alcohol consumption among 530 pregnant women was recorded retrospectively from the last menstrual period to a mean of ten gestational weeks, and thereafter prospectively to term. Fifty-five percent of women had drunk alcohol (average 66 g of ethanol) during the week when ovulation was assumed to have taken place. This was not significantly different from the figures in 100 women seeking contraception, of whom 72% drank on average 61 g of ethanol during the ovulation week. Ninety percent of women drank alcohol at least once after the diagnosis of pregnancy. Drinking more than 600 g of ethanol during the first 12 gestational weeks (about four drinks weekly) was associated with an increased frequency of preterm delivery (P less than .05), but fetal outcome was not compromised. The proportion of drinking women decreased with advancing gestational age, with only 50% drinking after 32 weeks and only 20% during the last week of gestation. Beer was most commonly consumed, followed by wine and liquor. Alcohol consumption during pregnancy ranged between 7 and 4440 g, but 90% of the subjects drank less than 1100 g (zero to two drinks per week). Thus, women tended to decrease their drinking during pregnancy. Fewer than two drinks weekly had no detectable adverse effects on the fetal outcome.