The Superhuman Mind

Cases of extraordinary mental ability

Good Mothers Don't Drink

Even one alcoholic drink during pregnancy can significantly lower a child's IQ

Fetal alcohol syndrome (FAS) is a condition associated with mental and physical developmental defects caused alcohol intake during gestation. Children with FAS may exhibit deformed facial features including skin folds at the corners of the eyes, a small mid-face and short nose, a small upper lip and an indistinct philtrum (the groove between the upper lip and nose). Structural, neurological and functional central nervous system deficits are also observed in children with FAS. This not only has an effect on cognition but also on organ function since the brain may not appropriately regulate such processes as heart rhythm, voluntary muscular movement or even vision. These defects have a profoundly negative emotional effect on the victims of this condition. Unlike a lot of other children who have genetic deficits that may present in similar ways to FAS, children of this condition grow up knowing their lives could have been different if only their mothers had not consumed so much alcohol.

We know that heavy alcohol consumption during pregnancy causes FAS, but there currently is no consensus on just how much alcohol consumption may be permissible during pregnancy, if permissible at all. To be on the safe side, the U.S. Surgeon General recommends that mothers avoid the consumption of any alcohol during pregnancy. However, popular belief is that occasional consumption of alcohol has no negative affects on fetal development. Surveys have found that between ten and fifteen percent of American women report recently having consumed alcohol, and up to thirty percent have consumed alcohol at some point during pregnancy.

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A few studies have appeared to support the belief that it is okay to occasionally drink. One recent systematic review found no consistent evidence of negative effects caused by moderate alcohol consumption. At least one other study found that mothers who completely abstain from alcohol consumption during pregnancy might have certain personality traits thought to be disadvantageous to the child’s emotional development. Moderate alcohol consumption is associated with the ability to manage stress. Studies have shown a positive correlation between moderate alcohol association and life expectancy. Some mothers just need to learn to “relax.”

However, a recent study conducted by Sarah Lewis et al. at the University of Bristol shows that alcohol consumption has far more deleterious effects on child development than once thought. Although they may not exhibit obvious mental and physical defects, children exposed to even a minimal amount of alcohol during gestation may suffer from cognitive deficits later in life. Alcohol is metabolized by the body with a series of five enzymes called alcohol dehydrogenases (ADH). Genetic differences among individuals is associated with varying abilities of the body to efficiently metabolize alcohol. While some individuals appear to metabolize alcohol very quickly, leading to reduced blood alcohol content (BAC), the BAC of other individuals may remain higher for a longer period of time. This inefficiency to metabolize alcohol is significantly correlated with alcoholism and drug abuse. It also means that a fetus is exposed to alcohol for a longer period of time.

Lewis and her colleagues had women complete a questionnaire at eighteen weeks of gestation, which asked them to describe their alcohol consumption before the pregnancy, during the first trimester and over the previous two weeks or the time they first felt the baby move. At 32 weeks, women filled out another questionnaire about their current alcohol habits in order to establish a rate of consumption for each woman. Any woman who reported drinking at all during the study were classified as drinkers and any women who had drank at least two pints of beer at one time were classified as binge drinkers. These classifications fall within the common medical understanding of moderate drinkers. The researchers also obtained genetic samples from each participant to study the genes that affect the production of ADH enzymes.

When the children of the mothers enrolled in the study were eight years of age, the researchers administered a shortened version of the Wechsler Intelligence Scale for Children (WISC-III), a standard IQ test. They found that children exposed during gestation to even moderate amounts of alcohol had IQs lower than those who were not exposed to alcohol at all. They also found a significant correlation between the efficiency of the mothers’ metabolism and IQs. This suggests that fetal alcohol exposure is due to the metabolism of alcohol rather than intake.

This study has important implications for how we must think about alcohol consumption during pregnancy. Mothers don't have direct control over fetal alcohol exposure. While one individual might have a particularly efficient metabolism and be able to consume a significant of alcohol without harming the fetus, other mothers suffering from an inefficient metabolism may harm the fetus by consuming as little as one drink. Anecdotal reports from mothers who drank moderately during pregnancy lead many of us to believe our children might still become geniuses despite fetal alcohol exposure. While there are always a few outliers, it is likely that even a minimal amount of exposure to alcohol can have adverse cognitive effects. Most parents do all they can to set their children up for success. They should start by abstaining from alcohol during pregnancy, for it would be a shame to limit the child’s cognitive abilities right at the start.


Lewis SJ, Zuccolo L, Davey Smith G, Macleod J, Rodriguez S, Draper ES, Barrow M, Alati R, Sayal K, Ring S, Golding J, Gray R. (2012). Fetal Alcohol Exposure and IQ at Age 8: Evidence from a Population-Based Birth-Cohort Study. PLoS One.

Kristian Marlow is a graduate student at the University of Missouri-St. Louis and a member of the St. Louis Synesthesia Lab.


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