Study: A Drink Per Day During Pregnancy Seems Safe

By Lindsay Abrams
Jing a Ling/Flickr

PROBLEM: The National Institutes of Health, along with most organizations in positions of authority, "strongly urge" pregnant woman to abstain from consuming alcohol. Heavy drinking during pregnancy is known to cause fetal alcohol spectrum disorders (FASDs), although the effects of minimal to moderate consumption -- and what would even constitute "moderate" -- are less clear.

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METHODOLOGY: One measure of a child's neurodevelopment, which could potentially be impacted by fetal exposure to alcohol, is his or her ability to balance. Researchers at the University of Bristol looked at the ability of 7,000 10-year-olds to: walk across a balance beam; stand still, heel to toe, on the beam for 20 seconds with their eyes open and then closed; and do the same on one leg.

The children were all born in the early nineties; halfway through pregnancy, their mothers had been asked about their current alcohol consumption, as well as about how much they used to drink before they became pregnant.  The researchers compared this to the children's performance on the balance test 10 years later, controlling for maternal age, smoking behavior, and caffeine consumption, and for less obvious measures like how often the father drank alcohol (which animal models suggest might be important to fetal health).

RESULTS: No significant differences were observed in the 10-year-olds' ability to balance based on their mothers' consumption of any amount of alcohol during pregnancy. In fact, the children of light drinkers did slightly better on the tests -- they were particularly good at standing still on two feet -- but the difference disappeared once the researchers took the families' socioeconomic class into consideration. 

Overall, about 70 percent of mothers reporting abstaining completely for the duration of their pregnancy, while 30 percent drank moderate amounts (defined as 3 to 7 glasses per week). Although almost none fell under the next category (more than one glass per day) or were considered binge drinkers (more than four per day). Generally, it was the more "socially advantaged" mothers, as determined by factors like their occupation, marital status, and home ownership, who drank during pregnancy.

IMPLICATIONS: A series of studies published last year failed to find any negative neurodevelopmental effects of moderate drinking (either 1 to 4 or 5 to 8 drinks per week) by age five. And this April, another study looked at development in 7-year-olds, and found no social, behavioral, or cognitive problems in children of light drinkers (this time, up to 2 drinks per week) as compared to children whose mothers abstained. This is one more outcome to appear unaffected at one more age, but it's still not the definitive word on drinking in pregnancy. The March of Dimes puts the stakes simply: "If you stay away from alcohol during pregnancy, your baby can't have FASDs or any other health conditions caused by alcohol."

The full study, "Prenatal alcohol exposure and childhood balance ability: findings from a UK birth cohort study," is published in the journal BMJ Open.

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