Is moderate drinking during pregnancy associated with an increased risk for malformations?

The relationship between heavy drinking during pregnancy and congenital malformations is well known; however, whether moderate or light drinking is teratogenic is controversial. This prospective birth defects study collected information from 32,870 women about alcohol consumption during the first trimester of pregnancy. Total malformation rates were not significantly higher among offspring of women who had an average of less than one drink per day (77.3/1,000) or one to two drinks per day (83.2/1,000) than among nondrinkers (78.1/1,000). An increased risk as small as 12% in the group averaging less than one drink per day and 45% in those averaging one to two drinks per day would most likely have been detected if it were present. Likewise, major malformations were not increased in these drinking groups. Examining malformations by organ system and individual defect revealed that sex organ malformations and all genitourinary malformations increased significantly (P less than .05) with increasing alcohol consumption. These findings suggest that alcohol, at the levels usually consumed during pregnancy, is not a significant cause of malformations. Nonetheless, the possibility that there are some malformations for which no safe drinking level exists requires additional investigation.