A new review study out Tuesday has a sobering conclusion for pregnant women: Drinking alcohol will increase the risk of your child being born with cognitive problems and lower birth weight.
Public health agencies like the Centers for Disease Control and Prevention have long recommended that women avoid drinking alcohol at any point during pregnancy, citing the increased risk of fetal alcohol spectrum disorders. These disorders have a variety of symptoms, from learning disabilities to heart, lung, and bone issues.
But much of the evidence that shows alcohol’s harm to human fetuses is observational, meaning studies track groups of people over time in the real world. These studies, important as they are, can’t prove a direct cause-and-effect relationship. There are also still questions about whether light alcohol use, particularly later on in pregnancy, poses any real health risks.
To get a better grasp on the topic, the authors of the new review, published in the International Journal of Epidemiology, took a different tack. They looked at a randomized clinical trial studying alcohol use in women as well as other types of studies that might be better able to show a direct link between the two factors.
One study, for instance, recruited pregnant women in a trial where different methods were used to help them drink less. Other studies looked at what happened to children born to younger mothers in an area before and after the minimum drinking age was lowered—providing a sort of natural experiment. Two studies compared siblings where the mother’s drinking level had changed in between pregnancies. All told, they looked at 23 studies, finding a clear link between prenatal alcohol exposure and worse cognitive health, as well as a connection to lower birth weight.
“It is when results from more than one study type point in the same direction, like we found for birthweight and cognition, that we are more confident that they are robust and not a fluke, caused by some error or factors other than alcohol,” lead author Luisa Zuccolo, an epidemiologist at the University of Bristol, told Gizmodo via email.
These studies all have their benefits and drawbacks. And the authors can’t quantify the difference in risk a women’s alcohol use will have on a pregnancy based on this review alone. A previous review by the authors had concluded that telling women to avoid even light drinking was more of a precaution than a recommendation backed by concrete evidence. But their new findings, they argue, tip “the balance towards a more solid evidence base” for complete abstinence during pregnancy.
“We remain a little way off being able to quantify just how harmful alcohol is for varying levels of drinking, particularly low levels,” Zuccolo said. “However what this study shows is that the claims of a causal effect are stronger. Since most of the mothers included in the various data sources that we reviewed were at most moderate drinkers, we know that the effects weren’t just driven by excessive drinking. But we can’t say much more than this for now.”
In the UK, where the researchers are based, alcohol abstinence has been promoted through catchy-sounding social media campaigns in the past few years. Dry January, a trend that began in 2013, was an idea from the UK charity Alcohol Change, for instance. The UK government has similarly coined #DRYMESTER as a new health awareness campaign for pregnant women, which the authors wholeheartedly support.
“Our study reinforces the UK Chief Medical Officers’ guideline: DRYMESTER (abstaining in all trimesters) is the only safe approach,” Zuccolo said in a statement provided by the university. “This message is more important than ever, given recent research which shows the alcohol industry promoting confusing information about the real health implications of drinking during pregnancy.”
Indeed, the alcohol industry has a shady record of promoting unsafe ideas. In 2018, an Australian alcohol industry group angered public health organizations when it distributed posters to hospitals that read, “It’s not known if alcohol is safe to drink when you are pregnant.”
Meanwhile, in the U.S., alcohol is killing more Americans than ever.
This article has been updated with comments from the study’s lead author.