Alcohol use during pregnancy contributes to many problems in exposed children. Heavy prenatal alcohol exposure leads to fetal alcohol syndrome, a devastating birth defect characterized by craniofacial malformations, neurological and motor deficits, intrauterine growth retardation, learning disabilities, and behavioral and social deficits. Most women who drink alcohol during pregnancy, however, are light-to-moderate drinkers in early pregnancy and quit or decrease their alcohol use by mid-pregnancy. In this long-term study, researchers examined effects of lower levels of prenatal alcohol exposure. They specifically focused on the relation of prenatal alcohol exposure to a subsequent diagnosis of conduct disorder during childhood.  Conduct disorder is a pattern of aggressive, destructive, or unlawful behavior problems. The study sample included 592 adolescents and their mothers. Women in the study were interviewed at their fourth and seventh prenatal months, and then at routine intervals post-partum until their children were 16 years old. The researchers found that children who had been exposed to an average of one or more drinks of alcohol per day in the first trimester of pregnancy were three times more likely to meet criteria for a diagnosis of conduct disorder than were adolescents whose mothers drank less than that amount or abstained.