Imagine this scenario: A couple goes on a Caribbean cruise with an all-you-can-eat buffet and an open bar. During the trip, they engage in 2 or 3 days of binge-style drinking, which is considered about four drinks in a single sitting. A few weeks after the trip, the woman finds out that she’s pregnant and calls your office wondering if there will be any harm to the fetus.

This is not a theoretical question. I have received many of these calls over the years, and in some cases the fear of adverse effects on the baby has led the couple to terminate the pregnancy. When we consider the general rise in binge drinking in North America and the fact that about half of all pregnancies are unplanned, this is a very real concern.

The first step is to find out whether the binging occurred during the “none or all period” before implantation, or whether it happened after implantation, reaching the embryo, where the teratogenic risk becomes more tangible.

Unfortunately, the literature has not been clear on the long-term impact of binge drinking in pregnancy. Animal studies suggest that it is the peak in the alcohol level created by binge drinking that causes damage to the fetus, rather than a sustained level of alcohol (although that obviously carries risk as well). The literature in humans has been controversial.

One of the most recent studies is a prospective cohort study of more than 1,600 women and their children sampled from the Danish National Birth Cohort. The investigators collected information on maternal alcohol use in early pregnancy and examined children at age 5 years using the Strengths and Difficulties Questionnaire (SDQ) completed by the mothers and a preschool teacher. It found no statistically significant association between binge drinking in early pregnancy and child behavior at age 5 years (BJOG. 2013 Aug;120[9]:1042-50).

In this study, the investigators corrected for parental education, maternal IQ, prenatal maternal smoking and postnatal parental smoking, the child’s age at testing, the child’s gender, maternal age, parity, marital status, family-home environment, prepregnancy maternal body mass index, and the child’s health status. After adjusting for confounders, they found no association between binge drinking and scores on the SDQ (odds ratio, 1.2; 95% confidence interval, 0.8-1.7 for behavioral scores and OR, 0.8; 95% CI, 0.6-1.2 for total difficulties scores). Additionally, the investigators analyzed low to moderate weekly alcohol consumption in early pregnancy and also could not find a significant effect (OR, 1.1; 95% CI, 0.5-2.3 for behavioral scores and OR, 1.1; 95% CI, 0.6-2.1 for the total difficulties scores).

This finding received a lot of press attention at the time, but it’s not the only study that has shown a lack of effect from binge drinking in contrast to the conventional wisdom on this subject.

A meta-analysis published in early 2014 further adds to the literature on this topic (Alcohol Clin Exp Res. 2014 Jan;38[1]:214-26).

The meta-analysis showed a small, but statistically significant effect on child’s cognition associated with binge drinking in pregnancy (Cohen’s d [a standardized mean difference score] −0.13; 95% CI, −0.21, −0.05). It did not include the 2013 Danish study.

The meta-analysis examined other levels of drinking in pregnancy, not just binging. Out of more than 1,500 papers that were examined, 34 studies met the criteria for inclusion, and just eight were included in the binge drinking analysis. The eight studies comprised more than 10,000 children who were tested from ages 6 months to 14 years. The researchers analyzed eight functional domains: academic performance, attention, behavior, cognition, memory, language and verbal development, executive function, and visual and motor development.

The researchers also separated the studies based on quality. When they analyzed the results for only high-quality studies, the cognition effect was not significant and no other associations were found with other child neuropsychological outcomes.

Several other studies have examined different endpoints, particularly hyperactivity and externalizing behaviors. While several studies show a trend toward those effects, mothers who binge drink also tend to be more externalizing in their own behavior.

An examination of the literature shows just how difficult it is to produce clear results that inform clinical practice. Adjusting for confounding factors from marital status to maternal IQ is just one hurdle. Another area that plagues researchers is that knowledge of drinking in early pregnancy is based on self-reports, and it is nearly impossible to know for sure if the reports of binging are accurate and also if there has been chronic alcohol use.

So what does all of this mean when it comes to advising women? There is no question that women should be advised not to drink when they are pregnant or planning a pregnancy. For a woman who engaged in binge drinking before she knew she was pregnant, it’s difficult to say that there is no effect. Instead, the collective evidence suggests there may be a small effect on cognition. In cases where binge drinking has occurred, children should be monitored as early as possible for any potential developmental effects.

Dr. Koren is professor of physiology/pharmacology and pediatrics at Western University in Ontario. He is the founder of the Motherisk Program. He reported having no relevant financial disclosures. Email him at obnews@frontlinemedcom.com.

How great is the risk from binge drinking in pregnancy?