The subject of caffeine and miscarriages is a controversial one. While many studies do show a link between caffeine consumption and miscarriage, it is not clear that caffeine itself is the cause. This subject became even more difficult to resolve when one study found that consumption of decaffeinated coffee was linked to a higher risk of miscarriage than consumption of caffeinated coffee.
Decaffeinated Coffee and Miscarriage
A study published in the September 1997 issue of "Epidemiology" examined the relationship between miscarriages and the consumption of both caffeine-containing beverages and decaffeinated coffee. More than 5,000 women were interviewed during their first trimester of pregnancy and asked about their caffeine intake. An analysis of the data showed no significant link between caffeine consumption and miscarriage after adjusting for age, socioeconomic status, smoking and alcohol consumption. However, the researchers did find a link with the consumption of decaffeinated coffee.
Possible Explanations
A July 2003 article in the "American Family Physician" reported that nausea during pregnancy -- morning sickness -- is often a sign of a viable pregnancy. Conversely, women without nausea often have less viable pregnancies that are more likely to end in miscarriage. If women with more viable pregnancies avoided decaffeinated coffee because of morning sickness while women with less viable pregnancies felt well enough to drink it, a correlation between decaffeinated coffee and miscarriage would exist even though this beverage played no causal role in the outcome of the pregnancy. The "Epidemiology" researchers noted of this correlation, "Although we could not demonstrate this with available data, we suspect that this association was due to bias resulting from the relations among fetal viability, symptoms of pregnancy such as nausea, and consumption patterns during pregnancy."
Is It Really Morning Sickness?
A study published in the March 2008 issue of the "American Journal of Obstetrics and Gynecology" cast doubt on the theory that morning sickness explains the link between coffee and miscarriage. This study, which controlled for morning sickness, found that women who consumed 200 mg of caffeine daily had twice the rate of miscarriages as women who consumed no caffeine. This finding held true for all sources of caffeine, including tea and soft drinks, indicating that it was most likely caffeine, and not some other substance in coffee, that was responsible.
Decaffeinated Coffee Contains Caffeine
Decaffeinated coffee has substantially lower levels of caffeine than regular coffee, which averages 85 mg per cup, but it is not caffeine-free. In an October 2006 study published in the "Journal of Analytical Toxicology," researchers from the University of Florida measured the caffeine levels in decaffeinated coffees and found that several contained more than 10 mg of caffeine per serving, a dose that could add up to substantial amounts if a person drinks many cups per day.
References
- "Epidemiology"; Caffeinated Beverages, Decaffeinated Coffee, and Spontaneous Abortion; L. Fenster, et al.; September 1997
- "Journal of Analytical Toxicology"; Caffeine Content of Decaffeinated Coffee; R.R. McCusker, et al.; October 2006
- "American Journal of Obstetrics & Gynecology"; Maternal Caffeine Consumption During Pregnancy and the Risk of Miscarriage: a Prospective Cohort Study; Xiaoping Weng, Ph.D., et al.; March 2008
- "American Family Physician"; Nausea and Vomiting of Pregnancy; Jeffrey D. Quinlin, et al.; July 2003
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