BACKGROUND: In March 1999, the National Board of Health changed its recommendations about alcohol drinking in pregnancy. A "No drinking" policy was changed to three recommendations: 1. Avoid, as far as possible, alcohol in pregnancy; 2. Never take more than one drink a day; and 3. Do not drink alcohol every day. AIM: By means of data from the Danish National Birth Cohort, to monitor changes in pregnant women's reporting of alcohol drinking before and after the change in policy. METHODS: From October 1, 1997, to September 30, 1999, a total of 30,899 pregnant women were interviewed by the end of first trimester. Information on alcohol intake reported among women interviewed from July 1, to September 30, 1998 was compared with the same information obtained from interviews completed in the same months in 1999. RESULTS: Overall, there were no changes in mean alcohol intake in the two periods. Hence, the mean intake was 0.6 drinks per week in the period before and 0.7 drinks per week in the period after introduction of the recommendations. The proportion of women drinking more than two drinks per week was 6.4% before vs 7.4% after the new and less restrictive recommendations (p = 0.12). The proportion of women having one or more binge episode (e.g. drinking five or more drink at one occasion) was 26.7 vs 27.4 (p = 0.65). CONCLUSION: The study showed no significant changes in drinking habits among Danish pregnant women after relaxation of the guidelines for sensible drinking during pregnancy.