Light Drinking in Pregnancy OK?

Drinking up to one to two glasses of alcohol per week during pregnancy does not appear harmful to the baby, according to a new study.

The study, published yesterday in the Journal of Epidemiology and Community Health, by researchers from the University College London, is a retrospective study, which followed more than 11,500 children born between September 2000 and January 2002, using data from the UK Millennium Cohort Study. Mothers were classified as non-drinkers altogether, non-drinkers during pregnancy (but drinkers otherwise), light drinkers during pregnancy (i.e. one to two glasses of alcohol per week), moderate drinkers during pregnancy (3 to 6 glasses per week), and binge or heavy drinkers (7 or more glasses per week) during pregnancy. Mothers were interviewed about their child's behavior at age 3, and children were tested for behavior and cognitive development at age 5.

Children of mothers who were light drinkers during pregnancy were 30% less likely to show behavior problems than children of mothers who stopped drinking during pregnancy. When the study was corrected for socio-economic status and other factors, they effect still showed 23% advantage for children of light drinking mothers. Cognitive development was also higher for children of light drinking mothers, even after fully adjusting the study results for mediating factors. "There appears to be no increased risk of behavioral or intellectual problems in their children [at age 5]," says Dr. Yvonne Kelly, study investigator. In fact, says Dr,. Kelly, ""children born to light drinkers seemed to have fewer behavioral problems and higher cognitive scores than those born to moms who didn't drink during pregnancy."

What are the limitation of the study?

• The study is observational only (cohort study), and cannot prove causality - only a randomized double-blind trial could do that.
• There may be mediating factors that were not taken into account when compensating for other factors in the study.
• Subjects self reported their drinking, which may subject this measure to some self reporting bias.

Nevertheless, the sample was large (more than 11,500 children), and the methodology so far has in general not been criticized by outside experts.  In fact, a similar study published in June 2010 in the British Journal of Obstetrics and Gynecology, and  using 14 years' worth of data from the Western Australian Pregnancy Cohort (Raine) Study, reported similar results, not only for children of light drinkers, but also for children of moderate drinkers during the first trimester of pregnancy. "Children of light and moderate drinkers had less emotional and behavioral problems through childhood and adolescence," said Dr. Monique Robinson, from Telethon Institute for Child Health Research in West Perth, Western Australia, as reported in Reuters. 

These studies are not the only ones reporting no harm from light drinking in pregnancy. As early as 1991, Dr. Joel Alpert and Dr. Barry Zuckerman of the Boston University School of Medicine wrote, in the journal Pediatrics in Review, in an analysis of other studies: "Our conclusion is that there is no measurable or documented risk from this level [two or fewer drinks per day] of drinking during pregnancy."

Experts, however, were quick to point out that this study should not be seen as an invitation to drink. "I do not believe we want to establish a precedent that any level of alcohol consumption is okay, because in truth, we really don't know the long-term effects of even light drinking," commented Dr. Marc Lewis, service chief for Women's Health Services at Henry Ford Hospital in Detroit, Michigan, adding: "We know that in the United States, the leading cause of mental retardation is related to fetal alcohol syndrome." Dr. Timothy Naimi, an alcohol expert with Boston University School of Medicine, criticized the study: “These findings are highly implausible, given that ethanol is the world's leading fetal neurotoxin." "Fetal alcohol syndrome has been described in mothers who had a single episode of binge drinking," commented Dr. Ron Jaekle, professor of clinical obstetrics and gynecology at the University of Cincinnati.

What to conclude of all this? You should talk to your doctor before deciding what your drinking behavior should be during pregnancy. The general recommendation in the US is to fully abstain from drinking during pregnancy. It seems, however, from a preponderance of evidence, that light drinking, consisting of one to two glasses of wine or beer per week during pregnancy, is unlikely to cause any development or behavior problem to the child.

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Study Abstract