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Caffeine: Does it Affect Your Fertility and Pregnancy?

By Samuel A. Pauli, MD and Donna R. Session, MD
Published in Resolve for the journey and beyond, Winter 2009

Chocolate, coke, coffee, cappuccinos, espresso, lattes… the list goes on, let’s face it, Americans love caffeine. Caffeine is one of the most widely available drugs. The website coffeeresearch.org estimates that more than half of adults consume coffee daily and another quarter of adults are occasional drinkers. A matter of fact, a recent survey of more than 10,000 caffeinated beverage drinkers estimated the average woman of reproductive age consumes approximately 100 mg of caffeine a day with the top ten percent of caffeine drinkers exceeding an excess of 229 mg a day.

With such widespread consumption of caffeine, the potential health impact of caffeine use cannot be underestimated. Caffeine is a nervous system stimulant which helps provide that morning pickup for millions of Americans. However, caffeine also affects other organ systems of the body. Caffeine consumption is responsible for a rise in heart rate and blood pressure, revs up metabolism and increases urine formation.

Multiple studies have suggested that caffeine consumption increases the risk of miscarriage. A study published last year demonstrated an increase in the risk of miscarriage with increasing caffeine intake. Women consuming greater than 200 mg of caffeine per day had twice the miscarriage rate (25.5%) as compared to nonusers (12.5%). Moreover, pregnant women may be more sensitive to caffeine as it is metabolized or broken down slower during pregnancy. An additional concern in pregnancy is the ability of caffeine to cross the placenta and directly affect the developing baby.

While studies suggest the importance of limiting caffeine use during pregnancy, caffeine may also impact the ability to become pregnant. Several studies have shown that caffeine increases the length of time it takes to conceive. One study showed that women who drank more than one cup of coffee a day were half as likely to become pregnant per cycle as compared to women who consumed less. Another study in patients undergoing in vitro fertilization (IVF) demonstrated that women who consumed even modest amounts of caffeine (50 mg) were likely to have decreased live birth rates. While the exact mechanism by which caffeine affects fertility is unknown, the answer may be related to the ability of caffeine to influence the quality of the developing oocyte (egg). Preliminary studies in mice and monkeys suggest caffeine inhibits oocyte maturation. An immature oocyte does not fertilize and therefore is unable to produce a pregnancy.

With most studies indicating that the effects of caffeine are related to amount of caffeine consumed, it would seem prudent for women contemplating pregnancy to limit caffeine consumption. Thus some experts have suggested an arbitrary threshold of less than 100 mg per day. Caffeine intake may be derived from several sources including coffee, tea, soft drinks and chocolate (see Table). Women who consume large amounts of caffeinated beverages should taper their caffeine intake gradually to avoid withdrawal symptoms such as headaches, irritability, restlessness and nausea. Ultimately, as no “safe” level of consumption has been documented, the goal should be judicious consumption during the preconception period and during pregnancy to minimize any potential harmful effects.

Samuel A. Pauli, MD is a Clinical Fellow, Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics at Emory University School of Medicine. Donna R. Session, MD, Associate Professor and Chief, Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, at Emory University School of Medicine. For more information, contact Samuel A. Pauli, MD. at spauli@emory.edu or 404.778.3401.

Common Caffeinated Beverages Amount (ounces) Caffeine (milligrams)
Starbucks Grande Coffee 16 330
Starbucks Latte or Cappuccino 16 150
Plain Drip Coffee 8 95
Red Bull Energy Drink 8.3 76
Starbucks Espresso 1 75
Instant Coffee 8 62
Tea 8 47
Cola 12 29
Chocolate Cake 8 25
Dark Chocolate Bar 1.55 21
Milk Chocolate Bar 1.55 9
Chocolate Ice Cream 8 4
Decaf Coffee 8 2

(Sources: Starbucks Corp., 2009; USDA National Nutrient Database for Standard Reference, 2008)