1-2 Drinks a Week Can Raise Miscarriage Risk

Drinking even a small amount of alcohol could increase the risk of miscarriage during the first four months of pregnancy, a new study from Denmark suggests.

Researchers used data from nearly 93,000 pregnant women who were part of the Danish National Birth Cohort from 1996 to 2003.

They found that women who had two drinks a week had 1.5 times the risk of miscarriage as those who didn't drink at all.

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"In our study, we were surprised to find that there was no safe lower limit of alcohol," said Dr. Anne-Marie Nybo Andersen, lead author of the study and an epidemiologist at the University of Copenhagen. "Even one drink per week increased the risk of miscarriage."

The study was published Jan. 9 in the International Journal of Epidemiology.

Experts recommend avoiding alcohol

Whether occasional drinking during pregnancy poses health risks, and if there is a "safe" amount of alcohol have been debated. While heavy drinking during pregnancy has been linked with certain birth defects, the effects of light or moderate drinking remain unclear. Still, major physician groups in the U.S. recommend against drinking at all during pregnancy.

Miscarriages occur in about 15 to 20 percent of pregnancies, according to the American College of Obstetricians and Gynecologists, and most occur during the first three months of pregnancy.

Andersen said her study shows that women should avoid alcohol during pregnancy. 

"If our risk estimates are correct, it's best not to drink at all," she said.

Dr. William McCarran, an intensive-care physician at the Children's Hospital of Pittsburgh, agreed.

"I don't think there's any benefit in drinking during the first trimester," said McCarran, who was not involved with the study.

He also said he recommends that women avoid drinking throughout their entire pregnancy, because of potential risks for birth defects that could happen later in pregnancy.

Heavy drinking doubles the risk

Researchers surveyed mothers on the amount of alcohol they drank weekly during the first four months of pregnancy.

They also asked mothers how often they smoked and drank coffee, their occupation and their reproductive history.

Mothers were categorized into four groups, based on the average number of alcoholic drinks they reported having per week: no drinks per week, one-half to one-and-one-half drinks per week, two to three drinks per week and more than four drinks per week.

Andersen and colleagues found a slight increased risk for miscarriage — about 5 percent — in women who had fewer than two drinks a week, compared with those who didn't drink at all. However, they found a 66 percent increased risk in women who had two to three drinks a week.

Women who had more than four drinks a week more than doubled the risk of miscarriage.

McCarren noted that the study doesn't demonstrate cause and effect, but it does show a link to an increased risk. "This study looks at a large population of patients," he said.

"It strongly suggests that if you're a woman who's trying to get pregnant or already pregnant, you might be putting your baby at risk," he said.

Pass it on: Light to moderate drinking during pregnancy might increase the risk of miscarriage. 

Editor’s note: This article was updated on August 17, 2022 by Live Science contributor Alice Ball following the Supreme Court's decision to overturn Roe v. Wade on June 24, 2022. This decision eliminated the constitutional right to abortion that was established by the 1973 court case and later affirmed by a 1992 case called Planned Parenthood of Southeastern Pennsylvania v. Casey. If you are seeking guidance and support on abortion, you can find information here at Live Science.