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Study Shows Link between Caffeine, Miscarriage

Teresa Shaw |28, January 2008


Study Shows Link between Caffeine, Miscarriage

Coffee, tea, soda and hot chocolate all present risk.

A new study shows that high doses of daily caffeine during pregnancy cause an increased risk of miscarriage. The study, published in the American Journal of Obstetrics and Gynecology, reports that caffeine obtained from coffee, tea, caffeinated soda and hot chocolate can increase the chance of miscarriage.

Many doctors warn against excessive consumption of caffeine in pregnancy, although the actual safe amounts vary. Many women abstain or cut back from caffeine upon learning that they are pregnant.

This study strengthens the association between caffeine and miscarriage risk because it removes speculation that the association was due to reduced caffeine intake by healthy pregnant women, said De-Kun Li, MD, Ph.D., a reproductive and perinatal epidemiologist with the Kaiser Permanente Division of Research and lead investigator of the study.

To address that speculation, the study, which included 1,063 pregnant Kaiser Permanente members from October 1996 through October 1998, examined the caffeine effect among women who never changed their pattern of caffeine consumption during their pregnancy.

Women who consumed 200 mg or more of caffeine per day (two or more cups of regular coffee or five 12-ounce cans of caffeinated soda) had twice the miscarriage risk as women who consumed no caffeine, Li said.

The study reports that increased risk of miscarriage appeared to be due to the caffeine itself; caffeine intake from non-coffee sources such as caffeinated soda, tea and hot chocolate all showed a similar increased risk of miscarriage.

The main message for pregnant women from these findings is that they probably should consider stopping caffeine consumption during pregnancy. This research provides clearer and stronger evidence that high doses of caffeine intake during pregnancy can increase the risk of miscarriage, said Li.

Caffeine has been suspected to be harmful to a fetus for some time. Caffeine crosses through the placenta and can be difficult for the fetus to metabolize. Caffeine also may influence cell development and decrease placental blood flow, which can lead to an adverse effect on fetal development.

Women in the study were asked about their intake of caffeinated beverages as well as the type of their drinks, timing of initial drink, the frequency and amount of intake, and whether they changed consumption patterns since becoming pregnant.

Pregnancy outcomes at up to 20 weeks of gestation were determined for all participants.
Overall, 172 of women in the study (16.18%) miscarried. No consumption of any caffeinated beverages during pregnancy was reported by 264 women (25%); 635 women (60%) reported 0-200 mg of caffeine intake per day; and 164 women (15%) had 200 mg or more of daily caffeine consumption.

Critics had maintained that the association was not so much a high dose of caffeine intake that increased the risk of miscarriage, but that women with a healthy pregnancy are more likely (than those about to miscarry) to reduce their caffeine intake due to nausea, vomiting, and aversion to caffeine, Li said.

Therefore, the critics claimed that the observed association was a result of reduction of caffeine intake by healthy pregnant women, he said.

However, many women turn to sodas or other caffeinated beverages during their pregnancy to quell morning sickness.

"I never consumed more than one can per day, but I did drink it whenever I felt nauseous, which was frequently", said Sharon Moran, the mother of a very energetic five-year-old. "The first 14 weeks, I vomited daily, and when I wasn't vomiting I had a general feeling of nausea. I drank Coke to soothe my stomach. I didn't always finish the entire can, but on a regular basis during the first trimester I would drink either Coke or ginger ale to settle my stomach."

So how should a tired mom-to-be cope with fatigue and nausea without a java jolt?

"If you definitely need caffeine to get you going, try keeping it to one cup or less a day," said Tracy Flanagan, MD, Director of Women's Health, Kaiser Permanente Northern California. Avoiding it may be even better, she said, or drink non-caffeinated sodas.

Learn to perk up instead with natural energy boosts like a brisk walk, yoga stretches, and snacking on dried fruits and nuts.

As for the nausea, ginger ale and hard candies can help to soothe an upset stomach. Check with your doctor if your nausea is severe to see about anti-nausea medications that are safe during pregnancy.

Find out how much caffeine is in your beverage with Energy Fiend's caffeine database

Teresa Shaw is a professional editor and freelance writer with a degree in English and journalism. She writes about motherhood, travel, and cooking, among other topics, for a variety of print and online markets. She enjoys spending time with her husband, daughter, two cats, and dog. Visit her online at Photo Courtesy of

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