November 22, 2017
Expecting woman with red wine in right hand

Is Some Alcohol Okay in Pregnancy?

by Berkeley Wellness  |  

Readers occasionally ask us if it’s okay to drink “just a little” during pregnancy. Despite decades of research, the answer is still muddled. Study conclusions are all over the place, which has led both health professionals and lay people to take different positions. A popular book, for example, stirred up controversy in 2013 by saying that pregnant women can have up to two drinks a week during the first trimester and up to one drink a day in the second and third trimesters. According to the CDC, however, “There is no known safe amount of alcohol use during pregnancy or while trying to get pregnant. There is also no safe time during pregnancy to drink.”

Research on alcohol in pregnancy

When a woman drinks during pregnancy, the developing fetus drinks too, since alcohol easily crosses the placenta. Alcohol exposure during fetal development has been linked to low birth weight, preterm births, and birth defects. It may also affect the brains of children years later. "Fetal alcohol spectrum disorders" is an umbrella term for a group of physical, mental, and behavioral conditions associated with the children of mothers who drink during pregnancy, the most severe of which is fetal alcohol syndrome.

It may not even take a lot of alcohol to cause problems. A 2014 paper in the Journal of Epidemiology and Community Health linked drinking—especially during the first trimester and even at low levels (two or fewer drinks a week)—to increased risk of low birth weight and preterm delivery. And a meta-analysis of studies, published in Alcoholism: Clinical and Experimental Research in 2014, found that even “mild” drinking during pregnancy (less than one daily drink) can negatively affect child behavior. Some researchers believe the risks of prenatal drinking are underestimated, with effects that may be permanent even from low consumption.

On the other hand, a number of studies have not reported any major problems at lower alcohol intake, including two papers from Denmark in 2012, which found that low (1 to 4 drinks per week) or moderate (5 to 8 drinks per week) alcohol consumption by pregnant women had no effect on children’s IQ at age five. Another study, from the UK in 2012, additionally found no behavioral deficits in children of light drinkers (1 to 2 drinks a week) at age five. Interestingly, some research has reported an association between drinking during pregnancy and better behavior and emotional development in children. Also contrary to other research, low to moderate prenatal alcohol consumption was not associated with low birth weight or preterm delivery in a 2014 study in Annals of Epidemiology. Still, the authors of these studies say their findings do not provide sufficient evidence to give a green light to drinking even a little during pregnancy.

Prospective Dads and Alcohol

While women are advised to stop drinking when trying to conceive and during pregnancy, most men don’t think twice about imbibing when they may become fathers. But maybe they should.

Why such inconsistencies?

For obvious reasons, researchers can’t conduct clinical trials in which women are randomly assigned to drink alcohol during pregnancy or abstain. Instead, they do observational studies in which they simply follow expectant moms to see how pregnancy outcomes correlate with drinking behaviors. But such studies do not prove cause and effect. For one thing, the researchers may not control for all factors that influence children’s health, such as other lifestyle habits and the psychological health of the mothers. As some studies have noted, mothers who drink (but don’t binge) during pregnancy tend to be older and better educated and have healthier lifestyles in general.

Studies that use self-reported alcohol intake, as these do, can also be problematic since they rely on the mothers’ memory and honesty in answering questions about their drinking history during pregnancy. And because studies use different methodologies and different definitions of light, moderate, and heavy drinking, they are hard to compare. Moreover, people vary in how they metabolize alcohol, which can affect the fetus—and there may be genetic variations in how fetuses respond to alcohol.

Sober advice on drinking during pregnancy

Most women who drink a little during pregnancy give birth to healthy babies with no known impairments in childhood or beyond. You may even be the product yourself of a mother who drank throughout pregnancy, as was fairly common and accepted some decades ago (and still is in other countries).

But there’s still so much we don’t know about alcohol’s effect on a growing fetus and long-term health; light drinking may carry risks we can’t yet measure. If studies fail to detect adverse effects of prenatal alcohol exposure, that doesn’t mean they don’t exist. We prefer to err on the side of caution and advise women to abstain from alcohol not only during all three trimesters of pregnancy but also while trying to conceive, since they may not know when they might become pregnant. They would also do well, of course, to quit smoking, consume adequate folate (and other nutrients), and avoid illicit drug use and exposure to lead, mercury, and other industrial chemicals. In addition, they should review any medications they are taking with their health care providers.