Can Vitamins and Coffee Affect Miscarriage Risk?

When it comes to preventing pregnancy loss, couples are often faced with more questions than answers. The vast majority of miscarriages are unexplained and unpreventable, though research over the years has tried to isolate factors more or less likely to increase risk of loss. That has led to ping-ponging advice over the role that alcohol, smoking, exercise, stress and daily vitamins, for instance, play in the outcome of a pregnancy.

In the latest study published in Fertility and Sterility, researchers looked at caffeine intake—including dad’s—and multivitamin use. They studied both the women and men in 344 heterosexual couples who became pregnant. The couples used home pregnancy tests to track their pregnancy, and agreed to keep daily journals of how much they smoked, how much alcohol they consumed, and how much caffeine they drank, starting from before they became pregnant until the time they got a positive pregnancy test.

Among them, 28% miscarried.

Women taking multivitamins daily, regardless of how much caffeine they drank, saw a 55% lower risk of pregnancy loss than those not taking vitamins. The Centers for Disease Control already recommends women take multivitamins that contain folate to lower the risk of neural tube defects in their babies. But this data also supports taking multivitamins to reduce miscarriage as well.

“When it comes to preventing miscarriages, there’s a lot of ‘don’t do this’ and ‘don’t do that,’” says Katherine Sapra, a post doctoral fellow at the National Institute of Child Health and Human Development and a co-author of the study. “There’s not a lot of what women can actually do to reduce their risk. Here we find that women can basically halve their risk of miscarriage by taking a vitamin every day.”

MORE: Women Now Have As Many Miscarriages As Abortions

The researchers also looked at caffeine. It was long thought that caffeine may influence a woman’s ability to stay pregnant, but many of those analyses have subsequently been disregarded. As such, many doctors now say up to four cups of coffee per day is perfectly safe for women at all stages of pregnancy.

In the new paper, scientists have data that suggests—but doesn’t prove—that more than two cups of caffeinated beverages a day may increase miscarriage risk. Once they accounted for the role that the woman’s age plays in miscarriage, the researchers found that the amount of caffeine that each partner drank daily had the strongest connection to pregnancy loss. This suggests caffeine may increase risk for pregnancy loss, although how that may occur isn’t clear and was not the focus of the study.

MORE: Trying to Get Pregnant Soon After Miscarriage is a Good Idea: Study

Still, there are other factors that Sapra and her colleagues did not consider, which could also explain the miscarriages independent of the caffeine. They did not look at how much the women exercised, for instance, what they ate overall, how much they slept and how much stress and anxiety they reported. All of those could potentially influence miscarriage risk more strongly than how much caffeine couples drink.

Sapra also notes that in her study, the couples’ caffeine consumptions wasn’t monitored by the researchers; the women and men reported on how much caffeine they drank, and such self-reports, while a legitimate research tool, can be open to bias.

Such bias may have led to the fact that the researchers in this particular study did not find a connection between pregnancy loss and smoking or alcohol, for example. Or it could simply be a matter of numbers. Sapra says there was only a small number of men and women in the study who smoked or drank since they were trying to become pregnant and many avoided those behaviors out of concern that they would negatively impact their chances of conceiving.

Sapra stresses that for couples struggling to get pregnant, the findings don’t provide a prescription for a healthy pregnancy, but does hint at what things they can do to hopefully avoid miscarriage and improve their chances of staying pregnant.