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There always seems to be new research coming out suggesting a daily coffee habit is linked to a higher risk of miscarriage, stillbirth, low birth weight and even childhood cancer. Then a new study gets published, disputing those results.

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The great coffee-during-pregnancy debate: It's back.

Truth be told, it never really left. There always seems to be new research coming out suggesting a daily coffee habit is linked to a higher risk of miscarriage, stillbirth, low birth weight and even childhood cancer. Then a new study gets published, disputing those results.

No wonder people are confused. In fact, the conflicting advice and back-and-forth arguments seem to have caused some women to even question conventional wisdom about carefully limiting how much caffeine they consume during pregnancy. For instance, many women celebrated last year when a new book, Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong – and What You Really Need to Know, concluded that most of the research linking caffeine to pregnancy risks was flawed, and that having a three or four cups a day seemed to be harmless.

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But what if the studies aren't wrong? And what if the current guidance about how much coffee pregnant women should drink is too lax?

That is the issue being raised by the Center for Science in the Public Interest (CSPI), a high-profile Washington-based consumer advocacy group. The organization put the issue back in the spotlight last month when it publicly criticized the U.S. Dietary Guidelines Advisory Committee for suggesting, in its latest draft guidelines, that pregnant women can safely consume up to 200 milligrams of caffeine a day (about one or two cups of coffee). CSPI argues that research published in recent weeks points to a higher risk of low birth weight, miscarriage and childhood leukemia among women who consumed as little as 100 milligrams a day. CSPI is staunchly opposed to the 200-milligrams-a-day guideline, and says going forward with the recommendation could cause serious problems for many pregnant women.

Here in Canada, the recommendations are even less restrictive. Health Canada, in concert with other health organizations, set the limit at 300 milligrams of caffeine a day, or the amount in about two to three cups of coffee.

In its criticism, CSPI cites a recent study in the European Journal of Epidemiology that found women who consumed 100 milligrams of caffeine a day had a 14-per-cent higher risk of miscarriage and a 19-per-cent higher risk of stillbirth.

That certainly sounds alarming. But the European study didn't establish a cause-and-effect relationship between caffeine and adverse outcomes. To do that, scientists would have to conduct a randomized controlled trial in which one group of pregnant women are assigned to consume a certain amount of caffeine a day while another group has none. That kind of study would go well beyond ethical boundaries, so it won't be performed. And that's why the debate over the risks will likely never end.

What might change, however, is the attitude around what should be considered "safe." Numerous studies have pointed to possible links between even small amounts of caffeine and miscarriage, stillbirth or low birth weight. The fact that it's difficult to quantify those risks or determine their true extent does not justify ignoring the need for some caution around caffeine.

Dr. Adam Urato, a maternal-fetal medicine specialist at Tufts Medical Center in Boston, says that "as a society, we've become too cavalier – too relaxed – about the issue of chemical exposures in pregnancy." He also said we've forgotten that caffeine is a chemical: Our attitudes toward it and other products, such as over-the-counter drugs, for instance, have perhaps become too permissive.

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"It's almost become the norm for people to be on multiple drugs," Urato said. "It carries over into pregnancy."

The problem with daily guidelines such as the 300-milligram-a-day caffeine limit in Canada is they convey the message that any amount of caffeine up to that point is safe. While Urato said there is "no cause here for widespread panic," he cautioned women to hear the message that limiting caffeine intake is a good idea. He advises his patients to cut back their coffee consumption as much as they can. It's a completely reasonable approach, one that underscores the potential risks without causing unnecessary fear.

This discussion will continue as long as pregnant women enjoy – or depend – on their daily caffeine habit. But there's more than enough evidence to persuade anyone that the cautious approach is the best one to take.

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