We examined the association of maternal drinking before and during early pregnancy on infant birthweight, using data collected from a population-based cohort in Avon Country, England. Participants completed several self-administered questionnaires during their index pregnancy. Our analysis included 10,539 women who provided drinking data and delivered a liveborn singleton child. Infants born to women who reported drinking one to two drinks daily with at least one binge, or three or more drinks daily with or without binges, had an adjusted mean birthweight approximately 150 gm less than that of infants whose mothers reported abstaining during (but not before) pregnancy. Mean birthweights were similar for infants of prepregnancy drinkers who drank weekly in early pregnancy, less than weekly, or not at all.