The question remains: is “light” drinking during pregnancy okay?

Well, it’s been a year of controversy and debate in the world of alcohol and pregnancy. It was about this time last year that a group of UK researchers published a study suggesting that low levels of alcohol consumption during pregnancy was okay, even possibly beneficial for male infants. This led to a flurry of media attention and focus on the subject.

Since then, there has been heaps of discussion: physicians publicly giving conflicting advice, TV episodes exploring “What would you do if you saw a pregnant women drinking in a bar?”, criticism of celebrities drinking wine during pregnancy, mommy blogs where women are bravely declaring that they drank during pregnancy and everything worked out okay, political discussion about warning labels on alcohol bottles in many provinces and countries, observations on the involvement of the alcohol industry in alcohol education, and public health officials resolutely believing that women just need to understand the risks of alcohol use better in order to abstain during pregnancy…. Sometimes it’s nice to take a break from the world of opinions, emotions, and political maneuverings and take a look at the latest research evidence.

Colleen O’Leary and Carol Bower, two researchers from Australia, published a paper last week in the journal Drug and Alcohol Review called “Guidelines for pregnancy: What’s an acceptable risk, and how is the evidence (finally) shaping up?” which I thought was a pretty balanced update on the current state of the research evidence.

O’Leary and Bower took a look at all systematic reviews and meta-analyses on low and moderate levels of prenatal alcohol exposure and all articles on the topic published in 2009-2010 after these reviews were published. They do an excellent job examining the methodological strengths and weaknesses of various studies and explain how beneficial outcomes of drinking alcohol during pregnancy (e.g., males may benefit from prenatal alcohol exposure) are likely related to methodological issues such as confounding and/or misclassification of exposure or outcome.

The authors conclude that there is no strong research evidence of harmful fetal effects from low levels of alcohol. However, these findings need to be placed in context:

  1. There are possible harmful effects at low levels of alcohol consumption that cannot be detected by current research methods.
  2. Harmful effects are well-documented with heavy exposure and moderate levels of exposure, e.g., 30–40 g per occasion and no more than 70 g per week. However, these numbers describe harms in the population at large and do not apply to individual women. The actual risk for an individual woman is influenced by things like genetics, nutritional status, other substance use, whether the fetus is male or female, etc. There might be a safe threshold for drinking, but we can’t know what that is for an individual woman.
  3. The evidence for harmful effects is very strong for moderate and high levels of alcohol use, i.e., 30–40 g per occasion and as little as 70 g per week. This translates to approximately 2 to 2.5 serves of wine or full-strength beer once or twice per week. This is not very much and leaves little margin for error between low and moderate levels of alcohol use; we know from research in other areas that few people have a good sense of how much alcohol is contained in what they are drinking.

So the question is, then, should alcohol and pregnancy policies and guidelines recommend abstinence or advise that low levels are low risk? The authors comment: “With such a small margin before there is increased risk to the fetus, it would be morally and ethically unacceptable for policies and guidelines to condone consumption of alcohol during pregnancy.”

While the authors advocate for women to be advised that “the safest choice for pregnant women is to abstain from alcohol during pregnancy,” they caution that this message must be presented in a balanced manner:

“Over-interpretation of risk leading to comments such as ‘even one drink can harm your baby’ will generate more harm than good. If the abstinence message is mishandled, women who have consumed alcohol during pregnancy may, out of fear, not reveal their drinking. In particular, this fear may prevent women with alcohol-related problems from accessing antenatal and treatment services, potentially exacerbating any risk to the fetus from exposure to alcohol.”  (p.9)

 Reference

O’Leary CM and Bower C. (2011). Guidelines for pregnancy: What’s an acceptable risk, and how is the evidence (finally) shaping up? Drug and Alcohol Review, early on-line access. DOI: 10.1111/j.1465-3362.2011.00331.x PMID: 21955332