You've probably heard that even moderate amounts of caffeine can affect a woman's fertility by delaying conception. The truth is, no one's certain that's true.

An often-cited 1993 study compared women who didn't drink coffee to those who did. Women who had more than moderate amounts of caffeine -- the equivalent of three cups of coffee a day, or about 300 milligrams -- lowered their likelihood of conceiving by as much as 27 percent. What researchers actually measure in such studies is the time it takes a woman to conceive. That time to conception is 27 percent longer on average among the women in this study. Modest consumption appeared to have a slight effect as well: Women who drink only one to two cups daily lowered their chances of conceiving by 10 percent per cycle.

A Danish study followed 430 couples for three years and found that caffeine had a far less significant effect. Compared with women who had less than 300 mg of caffeine per day, those who consumed 300 to 700 mg of caffeine lowered their odds of conceiving by only 12 percent. Drinking more than 700 mg per day reduced their odds by 37 percent. The researchers assumed that anything less than 300 mg was the baseline, as most studies don't find a significant difference at these levels of caffeine.

Studies on lifestyle and fertility are often criticized for not taking all related factors into account. In fact, researchers at Harvard Medical School recently conducted a review of the literature and claimed that there was no convincing evidence that caffeine delays conception. For example, one study from the San Francisco Bay Area found that caffeine had no effect on a woman's odds of conceiving, and that moderate tea drinkers were actually twice as likely to conceive per menstrual cycle. Among smokers, drinking caffeine doesn't seem to hamper fertility any further than smoking already does, possibly because caffeine is metabolized faster among smokers.

So what should you believe? Maybe it's best to rely on your own judgment. If you've been trying to get pregnant for several months without success, and you've already given up alcohol and smoking, you may want to try limiting your total intake of caffeine from coffee, soda, and chocolate -- especially if you regularly get more than 300 mg a day. Although there's no compelling reason to swear off your morning fix and occasional latte, you might even prefer to give up caffeine entirely.

If you're in your 30s, and you've been trying to conceive for more than six months, it may be a good idea to consult your physician to find out if you or your partner might have a fertility problem. It's more common than you might think.

Studies since the 1980s show that small amounts of caffeine increase the percentage of mobile sperm in semen. (The speed of the sperm was unaffected). However, these studies were conducted by adding caffeine to sperm samples -- in real life, the effects of caffeine may be different.

One study published in the journal Human Reproduction looked at men whose partners were undergoing either in vitro fertilization (IVF) or gamete intrafallopian transfer(GIFT). Men participating in the study who increased their normal caffeine intake by the equivalent of one cup of coffee per day were found to have double and, in some cases, triple the odds of multiple gestations. Discussing this and other findings, the researchers concluded that the findings, if replicated, suggest that "couples undergoing IVF or GIFT might benefit from a reduced caffeine intake before the initial clinic visit."

The average person consumes about 120 mg of caffeine a day, which is a moderate amount. We get about 75 percent of our caffeine from coffee, 15 percent from tea, 10 percent from soda, and 2 percent from chocolate. Caffeine is a common ingredient in food, so 300 mg adds up more quickly than you might think. This chart lists a few common items that contain the stimulant. Tea and chocolate also contain other stimulants related to caffeine, called theophylline and theobromine, and these have an unknown effect on human fertility.

Approximate caffeine content in milligrams (mg)Coffee and tea

Coffee, brewed, 8 oz, 65-135 mg

Coffee, instant, 8 oz., 60-85 mg

Coffee, espresso, single 1 oz. shot, 30-50 mg

Starbucks coffee (tall 12 oz.) 375 mg

Starbuck latte (tall 12 oz) 35 mg

Tea, black, 8 oz., 20-110 mg

Tea, green 8 oz., 30-35 mg

Tea, iced 8 oz.,10-50 mg

Tea, instant 8 oz., 25-30 mg

Cocoa, 8 oz., 5-30 mg

Soft drinks

Coca cola, 12 oz. can, 34 mg

Diet Coke, 12 oz. can, 45 mg

Pepsi, 12 oz. can, 38 mg

Diet Pepsi, 12 oz. can, 36 mg

Sunkist or Dr Pepper, 12 oz. can, 41 mg

Barq's Root Beer, 12 oz. can, 22 mg

Mountain Dew, 12 oz. can, 55 mg

Sprite, 7-Up, Mug Root Beer, 12-oz can, 0 mg

Other foods

Ben and Jerry's Coffee Fudge Frozen Yogurt, 1 cup, 85 mg

Dannon Coffee Yogurt, 1 cup, 45 mg

Haagen-Daaz coffee ice cream, 1 cup, 58 mg

Chocolate, milk, 1 oz., 1-15 mg Chocolate, dark, 1 oz., 15-35 mg

Drugs

Anacin, 2 tablets, 64 mg

Excedrin, 2 tablets, 130 mg

Vivarin, maximum strength No-Doz, 1 tablet, 200 mg

If you're planning to cut back or give up caffeine altogether, you may prefer to avoid it during pregnancy as well. Many women develop a caffeine aversion when they're pregnant, so it may be an easy decision!

-- Deepi Brar is the multimedia editor at Consumer Health Interactive.

References

Last updated January 21, 2009
Copyright © 2002 Consumer Health Interactive

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