Just small amounts of alcohol during pregnancy can increase the risk of miscarriage, researchers warn.
They analyzed 24 studies conducted between 1970 and 2019 that included more than 231,000 pregnant women.
They found that drinking alcohol during pregnancy -- even small amounts -- increases odds of miscarriage by 19%. Among women who have fewer than five drinks a week, each additional drink a week during pregnancy was linked with a 6% higher risk of miscarriage.
"Since alcohol is one of the most common exposures in early pregnancy, it's critical to understand how consumption relates to miscarriage," said lead investigator Alex Sundermann, a doctoral student at Vanderbilt University School of Medicine in Nashville, Tenn.
"Adverse pregnancy outcomes, like fetal alcohol syndrome, are often associated in popular culture with heavy consumption. However, our meta-analysis indicates even a modest amount of alcohol use has a meaningful impact on miscarriage risk," she said in a university news release.
The review pointed to important gaps in knowledge, including how the timing of alcohol consumption during pregnancy relates to miscarriage risk.
A previous study found that most women quit drinking after finding out they're pregnant, but no studies account for how this affects miscarriage risk.
"Timing of alcohol exposure in pregnancy is undoubtedly meaningful but isn't well-studied," Sundermann said.
"The groundwork for fetal development is laid in those first weeks of gestation before pregnancy can be detected with a home test, and that is also the time when alcohol exposure is most prevalent. It's key that we understand the impact of consumption in those first weeks," she said.
Sundermann noted that 1 in 3 women experience miscarriage, but many never get answers about why their miscarriage occurred.
She emphasized the need for more research into risk factors for miscarriage.
"Most women are motivated to do anything they can for the health of their pregnancy. We want to provide this information to empower women to make the best decisions," Sundermann said.
The meta-analysis was recently published in the journal Alcoholism: Clinical and Experimental Research.
The March of Dimes has more on miscarriage.