Healthnotes Newswire (December 21 & 28, 2000)—Drinking beverages containing caffeine may increase the risk of miscarriage among non-smoking women, according to a study published today in the New England Journal of Medicine.¹

In this new study, Swedish women who miscarried during the first 12 weeks of pregnancy were found to have significantly higher consumption of caffeine compared with women who carried their pregnancies to term. This association was limited to women who did not smoke cigarettes. Non-smoking women who consumed 500 mg of caffeine per day, or roughly five cups of coffee, were twice as likely to suffer a miscarriage compared with women who drank less than one cup of coffee per day.

The new study also found that increased risk of miscarriage was found in women consuming as little of 100 mg of caffeine per day. This finding appears to indicate that there may be no “safe” amount of regular caffeine consumption during pregnancy.

One cup of coffee contains roughly 100 mg of caffeine, depending on how it is brewed (drip coffee contains the most caffeine and instant coffee the least). Black tea contains about 40–70 mg per cup, and a 12-oz. can of caffeinated soda may contain 30–55 mg of caffeine. Caffeine is also found in cocoa, chocolate, and certain over-the-counter medications.

Decaffeinated coffee and decaffeinated green and black teas contain only traces of caffeine. Interestingly, this study (which was funded by a grant from the National Soft Drink Association) found that coffee and tea consumption accounted for 99% of all caffeine intake. If caffeine consumption from soda and other sources was underestimated, the results of this study may be somewhat inaccurate.

Previous research on this subject has yielded mixed results, with some studies showing an increased risk of miscarriage in women who consume more caffeinated beverages^{2 3 4} and other studies finding little or no correlation.^{5 6 7} None of these studies, the new one included, has been definitive. Until the safety of caffeine in pregnancy can be conclusively proven, pregnant women should consider eliminating caffeinated beverage intake.