BACKGROUND: Consumption of high doses of alcohol on a single occasion (binge drinking) may harm the developing foetus and pregnant women are advised to avoid binge drinking while pregnant. We present characteristics of Danish women who binge drank in the pre-and post recognised part of their pregnancy. METHODS: During the years 1996-2002 approximately 100,000 pregnant women were enrolled into the Danish National Birth Cohort. Women with information on binge drinking, time of recognition of pregnancy, age, reproductive history, marital status, smoking, occupational status, pre-pregnancy BMI, alcohol consumption before pregnancy, and mental disorders (n = 85,334) were included in the analyses. RESULTS: Approximately one quarter of the women reported binge drinking at least once during pregnancy; most of these in the pre-recognised part of pregnancy. Weekly alcohol consumption before pregnancy, single status and smoking were predictors for binge drinking in both the unrecognised and recognised part of pregnancy. Moreover, binge drinking in the pre-recognised part of pregnancy was more common among women aged 25-29 years, who were nulliparous, well educated in good jobs or skilled workers. Binge drinking after recognition of pregnancy was more common among women who were unintended pregnant, multiparous unskilled workers, had been unemployed for more than one year, or had mental/neurotic disorder. CONCLUSIONS: In order to prevent binge drinking during pregnancy, health care providers should target their efforts towards pregnant women as well as pregnancy-planners. It is important to be aware that women who binge drink before versus after the pregnancy is recognised have different social characteristics.