This large population-based cohort of over 1500 women recruited in early pregnancy has provided data on the prevalence of the most common patterns of prenatal alcohol use, encompassing not only the critical period before pregnancy awareness, but also measures of pre-pregnancy drinking and drinking throughout pregnancy. A novel question about special occasion drinking in the measurement of PAE produced important information on binge drinking episodes which would have remained undisclosed in an otherwise best estimate of dose, timing and frequency of exposure [20]. The question was particularly valuable for alcohol use measured immediately prior to, or soon after conception. In this study, one in five women reported a binge episode in the time period before pregnancy awareness, a third of whom would not have been identified without the special occasion question.
