Studies Examine Effects Of Caffeine Consumption On Miscarriage Risk

Main Category: Pregnancy / Obstetrics
Also Included In: Nutrition / Diet
Article Date: 23 Jan 2008 - 5:00 PDT

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A study published Monday in the Journal of Obstetrics and Gynecology found that pregnant women who consumed 200 milligrams or more of caffeine daily -- the amount in two five-ounce cups of coffee -- were about twice as likely to miscarry as pregnant women who did not drink caffeine, the Washington Post reports.

For the study, De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente, and colleagues enrolled 1,063 women in the San Francisco area early in their pregnancies. The women were questioned in detail about their beverage consumption and whether they experienced nausea (Stein, Washington Post, 1/21). The study found that 12.5% of the 264 women who said they had not consumed caffeine had miscarriages, compared with 24.5% of the 164 women who consumed 200 milligrams of caffeine daily. The study found that the increased miscarriage risk was linked to caffeine consumption itself and not other risk factors, such as smoking habits or maternal age (Grady, New York Times, 1/21).

Second Study Yields Different Results

Another study, published in the journal Epidemiology, found that moderate consumption of caffeine early in pregnancy did not increase miscarriage risk, the Boston Globe reports. For the study, David Savitz, an epidemiologist at the Mount Sinai School of Medicine, and colleagues enrolled 2,407 women who were interviewed about their caffeine consumption during pregnancies. The study found that daily consumption of about 350 milligrams of caffeine prior to and in early pregnancy, and 200 milligrams closer to 20 weeks' gestation, did not increase the risk of miscarriage. "We weren't addressing women who drink eight cups a day; we were addressing maybe two cups a day, so there's a narrow conclusion you can draw," Savitz said, adding that the study "adds to the evidence suggesting that those levels of caffeine are not a concern but doesn't address higher levels of coffee consumption."

Mark Klebanoff, a pediatrician and epidemiologist at the National Institute of Child Health and Human Development, said he cannot explain the differing findings of the two studies but added that such studies are challenged by the fact that people process caffeine differently. According to Jorge Chavarro, research fellow at the Harvard School of Public Health, Li's study addressed a flaw in earlier studies by accounting for women who experience nausea. Nauseated women, who often develop a distaste for coffee, have a lower risk of miscarriage than those who do not experience nausea, the Globe reports. "If you only compare the caffeine intake of women who did and didn't miscarry, to some extent you're comparing women who had and did not have nausea" (Cutraro, Boston Globe, 1/21).

Reaction

The March of Dimes after reviewing Li's study decided that it would modify its guidelines on caffeine consumption, Janis Biermann, senior vice president of education and health promotion for the group, said. The group, which had said eight to 16 ounces of coffee daily was safe, now will recommend that pregnant women try to limit their daily caffeine intake to 200 milligrams or less, Biermann said. According to the Times, representatives of the American College of Obstetricians and Gynecologists and the American Society of Reproductive Medicine said their groups have not taken official positions on caffeine consumption (New York Times, 1/21).

Aaron Caughey, a perinatolgist at the University of California-San Francisco, said that based on Li's study, he would not recommend even "a cup a day" but noted that up to 80% of miscarriages occur due to chromosomal abnormalities that have nothing to do with a pregnant woman's behavior (Allday, San Francisco Chronicle, 1/21). "Just interviewing women ... does not strike me as the best way to get at the real scientific question here," Carolyn Westhoff -- a professor of obstetrics, gynecology and epidemiology at Columbia University Medical Center -- said, adding, "Moderation in all things is still an excellent rule. ... I think we tend to go overboard on saying expose your body to zero anything when pregnant" (New York Times, 1/21).

An abstract of Savitz's study is available online.

Broadcast Coverage

Three broadcast programs reported on the study. Summaries appear below.

• CBS' "Evening News": The segment includes comments from study author Tracy Flanagan, director of women's health at Kaiser Permanente Northern California, and a woman who had a miscarriage (Assuras, "Evening News," CBS, 1/21). Video of the segment and expanded CBS News coverage are available online.
  
  
• NBC's "Nightly News": The segment includes a discussion with NBC News' chief medical editor Nancy Snyderman about the study (Williams, "Nightly News," NBC, 1/21). Video of the segment is available online.
  
  
• NPR's "Morning Edition": The segment includes comments from Flanagan and a pregnant woman (Aubrey, "Morning Edition," NPR, 1/21). Audio and a partial transcript of the segment are available online.
  
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