Pregnant women should limit caffeine intake

by Mark Miller April 07, 2016 4 min read

Pregnant women should limit caffeine intake

Women should drink no more than 2 cups of coffee per day, a new study suggests. (Wikimedia Commons photo)

Recent news about caffeine, pregnancy and miscarriage is kind of confusing. A complex study from the National Institutes of Health and Ohio State University linked couple’s consumption of more than two caffeinated beverages a day to a risk of miscarriage. Just to be safe, women trying to conceive and pregnant women should limit caffeine intake.

A press release from the NIH says that the study did not attempt to prove a cause-and-effect link.

The press release seems pretty straightforward:

A woman is more likely to miscarry if she and her partner drink more than two caffeinated beverages a day during the weeks leading up to conception … Similarly, women who drank more than two daily caffeinated beverages during the first seven weeks of pregnancy were also more likely to miscarry.

However, women who took a daily multivitamin before conception and through early pregnancy were less likely to miscarry than women who did not. The study was published online in Fertility and Sterility.

For the current study, researchers compared such lifestyle factors as cigarette use, caffeinated beverage consumption and multivitamin use among 344 couples with a singleton pregnancy from the weeks before they conceived through the seventh week of pregnancy.

Pregnant women should limit caffeine intake

Contrast that with a report from Slate.com that states: “Don’t be fooled by the scary reports that drinking caffeine before conception causes miscarriages. There is zero evidence to suggest that women (or men, for that matter) need to give up caffeine before or while they’re expecting. If caffeine and miscarriages are causally related—and that’s still a big if—then the risk seems to apply only to women who drink more than two caffeinated drinks per day. If you want to be extra cautious while you’re expecting or trying to conceive, sure, forgo some of the caffeine you might normally have.

Just to be safe, The American Pregnancy Association states: “Due to conflicting conclusions from numerous studies, the March of Dimes states that until more conclusive studies are done, pregnant women should limit caffeine intake to less than 200 mg per day. This is equal to about one 12 oz cup of coffee.”

Details of the study

The researchers in the new study used a hazard ratio, a statistical concept that estimates the chance of a health outcome. In this study, a score of less than 1 indicated a reduced risk for a miscarriage when caffeine is taken daily, and more than 1 indicates an increased risk for pregnancy loss.

There were 344 pregnancies in the study population, 98 of which ended in miscarriage. Women age 35 or above had a miscarriage hazard ratio of 1.96, almost double the risk of younger women. The press release explains:

The study authors cited possible explanations for the higher risk, including advanced age of sperm and egg in older couples or cumulative exposure to substances in the environment, which could be expected to increase as people age.

Both male and female consumption of more than two caffeinated beverages a day also was associated with an increased hazard ratio: 1.74 for females and 1.73 for males. Earlier studies, the authors noted, have documented increased pregnancy loss associated with caffeine consumption in early pregnancy. However, those studies could not rule out whether caffeine consumption contributed to pregnancy loss or was a sign of an unhealthy pregnancy. It’s possible, the authors wrote, that these earlier findings could have been the result of a healthy pregnancy, rather than caffeine consumption interfering with pregnancy. For example, the increase in food aversions and vomiting associated with a healthy pregnancy led the women to give up caffeinated beverages.

Because their study found caffeine consumption before pregnancy was associated with a higher risk of miscarriage, it’s more likely that caffeinated beverage consumption during this time directly contributes to pregnancy loss.

“Our findings also indicate that the male partner matters, too,” Dr. [Germaine] Buck Louis said. “Male preconception consumption of caffeinated beverages was just as strongly associated with pregnancy loss as females’.”

Take a multivitamin

There was some good news in the study, however, because the researchers found that there was a reduce risk of miscarriage if women took a daily multivitamin. During the time before conception, the hazard ratio was only 0.45—what the press release calls “a 55-percent reduction in risk for pregnancy loss. Women who continued to take the vitamins through early pregnancy had a hazard ratio of 0.21, or a risk reduction of 79 percent.”

The researchers’ article cites other studies that found taking vitamin B6 and folic acid reduces the risk of miscarriage.

Slate.com says it’s possible the higher risk of miscarriage among the study’s subjects was because higher caffeine intake is associated with risky behaviors such as drinking and smoking. Scientists are pretty certain smoking cigarettes and drinking alcohol carry a risk for miscarriage, low birth-weight babies and even birth defects.

If you’re a couple trying to conceive, the U.S. Centers for Disease Control has a pretty comprehensive Web package called Preconception Health and Health Care.

Mark Miller
Mark Miller


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