Further, the results indicate pregnant mothers who consume considerably less than an average of one drink per day put their children at risk for growth deficits and that exposure, as early as the first trimester, increases that likelihood.
The study, in the October journal Alcoholism: Clinical and Experimental Research, is one of the first to follow the development of children with prenatal alcohol exposure into adolescence. Most previous findings have involved children who are younger, leaving doctors to wonder whether or not the effects of prenatal alcohol exposure would lessen after children passed through puberty.
"Our findings indicate timing is very important for prevention efforts," said principal investigator Nancy L. Day, Ph.D., professor of psychiatry, pediatrics and epidemiology at the University of Pittsburgh School of Medicine. "Children of mothers who drank at least one drink a day during their first trimester weigh up to 16 pounds less, on average, than children with no exposure."
In the study, Dr. Day found that by the age of 14, children whose mothers drank during pregnancy fell behind in weight, head circumference, height and skinfold thickness compared with those whose mothers abstained. The size of the growth deficits was directly related to the amount of alcohol consumed. The clinical implications for the children's long-term health are not clear, but the growth deficits could serve as a potentially permanent marker of prenatal alcohol exposure. This report did not look at impairments in IQ or other functioning.
The study is one of few that have followed children born to drinking mothers past early adolescence. Mothers were recruited for the study in their fourth prenatal month. These women were then interviewed at regular intervals throughout pregnancy, and then with their children after birth and as the children grew.
In the study, Dr. Day and her colleagues report there was a substantial decrease in alcohol consumption during pregnancy. Although 38 percent of the women drank one or more drinks per day prior to pregnancy, by the first trimester only 18.9 percent of them drank at the same rate. By the third trimester, only 4 percent reported drinking at the same level.
"The good news from this study is that most women stop or greatly cut down on drinking as their pregnancies progress," said Dr. Day. "The bad news is that the first trimester is an important one for a baby's future development and not all women come in this early for prenatal care. We, as a health care community, need to address this issue."
There were significant differences in alcohol use by race, income level and presence of an adult male in the household. In the first trimester, whites were more likely to drink heavily than were African Americans. However, the white women were more likely to decrease or abstain from drinking later in pregnancy, so that by the third trimester, heavy drinkers were predominantly African American. Monthly income level was lowest among the heavier drinkers and abstainers and highest among the light and moderate drinkers. Light drinkers had the highest proportion of males in the household. The effects of prenatal exposure were still significant after considering these differences.
The study is part of the Maternal Health Practices and Child Developmental Project, a longitudinal study of pregnancy outcomes.