Caffeine may perk you up mentally, but it could have the opposite effect on your fallopian tubes, leading researchers to wonder whether women who drink coffee, tea and soda may have a harder time getting pregnant.
Researchers at the University of Nevada examined this possibility — in mice, not women — and concluded that caffeine stymies specialized cells in the muscular walls of the fallopian tubes, which transport eggs from a woman’s ovaries to her uterus. The cells are responsible for squeezing the eggs along their journey; if they don’t allow the tubes to contract efficiently, the eggs can’t reach the womb, according to the research published last week in the British Journal of Pharmacology.
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“This provides an intriguing explanation as to why women with high caffeine consumption often take longer to conceive than women who do not consume caffeine,” Sean Ward, a professor in the School of Medicine at the University of Nevada, said in a press release.
Previous research linking caffeine and pregnancy rates and outcomes has been inconsistent. A 2010 study in Medical Science Monitor found no association between caffeine and pregnancy rates, but did note that the drug was detected in the follicular fluid surrounding a woman’s eggs. In 2002, a study in Human Reproduction looked at 221 couples and concluded that failure to achieve a live birth after a cycle of in vitro fertilization (IVF) was associated with caffeine intake of more than 50 milligrams a day. Women who limited their caffeine intake to less than 50 milligrams had increased IVF pregnancy rates compared with women who consumed more. The average cup of home-brewed coffee has about 100 milligrams of caffeine.
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“In my mind because the data is controversial, I would err on the side of caution,” says Alice Domar, director of mind/body services at Boston IVF, a private clinic affiliated with Harvard Medical School and Beth Israel Deaconess Medical Center.
Domar advises most women trying to get pregnant to limit themselves to a cup or two of coffee per day. She cites the 2002 IVF study to her patients with infertility, recommending that they keep their caffeine intake to 50 milligrams a day — about a cup of tea, a soda or five chocolate bars. (Of course, five chocolate bars may be inadvisable for reasons other than difficulty achieving pregnancy.)
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Above all, Domar advises common sense. After all, “our mothers smoked and drank and most of us are mentally intact,” she says.