People whose mothers drank three or more glasses of alcohol at any one time in early pregnancy have an increased risk of developing an alcohol disorder by 21 years of age, according to an article in the September issue of Archives of General Psychiatry.

Exposure to maternal drinking during early childhood has been associated with difficulties in thinking, learning and memory, as well as mental and behavioral problems. However, few studies have examined the link between drinking during pregnancy and a child’s later risk for alcohol dependence and other disorders, according to background information in the article.

Animal studies have provided extensive evidence of a link between exposure to alcohol before birth and early acceptance of alcohol. “Similar results replicated in human studies would carry considerable implications for public health intervention,” the authors wrote. “First, such studies would suggest that even small quantities of alcohol exposure, if consumed in a single session, may cause in utero neurodevelopmental changes that in turn may lead to the early onset of alcohol disorder in youth. Second, they would provide support for the role of a biological origin of alcohol disorders.”

Rosa Alati, PhD, from The University of Queensland, Herston, Australia, and colleagues explored whether maternal exposure to alcohol during pregnancy increased a child’s risk of developing alcohol disorders in 2,138 participants who were followed from birth to age 21 years.

A group of 7,223 mothers was originally interviewed at their first prenatal physician visit, between 1981 and 1984 in Brisbane, Australia. The mothers and children were assessed at birth and again 6 months and 5, 14, and 21 years later. Before pregnancy, in early (first 18 weeks) and late (last three months) pregnancy, and when their children were age 5 and 14, the mothers were asked how often they drank alcohol and the number of drinks consumed on any one occasion. Children were evaluated for alcohol disorders at age 21.

Of the 2,555 children who completed an assessment at 21 years, 640 (25 percent) met criteria for a diagnosis of alcohol disorder; 333 (13 percent) of those reported developing the disorder before age 18 and 307 (12 percent) reported onset between age 18 and 21.

In the final analysis, which included 2,138 individuals, those whose mothers drank more than three glasses of alcohol on any one occasion during early pregnancy were 2.47 times as likely to develop an early-onset (before age 18) alcohol disorder and 2.04 times as likely to develop a late-onset (between ages 18 and 21) alcohol disorder.

Drinking during other stages of pregnancy, including late pregnancy, also increased risk. These associations remained strong after the researchers considered other biological and environmental factors that may contribute to the risk of developing alcohol disorders.

Interactions between genetic factors and exposure to alcohol before birth may affect the development of the nervous system in ways that predispose children and adults to alcohol problems, the authors wrote: “Our findings support a biological contribution to the origin of alcohol disorders and suggest that greater attention should be given to the role of the programming effect of in utero alcohol exposure to the development of alcohol disorders in adulthood.”