Caffeine is a popular addictive stimulant used by millions of people worldwide and found in various foods, beverages and medications. Excessive caffeine consumption during pregnancy, particularly when combined with alcohol or tobacco use, could cause fetal harm or miscarriage.
Source
Pregnant women can expose their embryos to caffeine from a variety of foods, including coffee, tea, soft drinks, chocolate and coffee-flavored candies and ice cream, according to the March of Dimes.
The FDA requires that medications that contain caffeine such as those used for pain relief, migraine and cold treatment, and sleep prevention have labels that list how much caffeine they contain. Herbal medications such as guarana, yerba mate, kola nut and green tea extract can contain as much and in some cases eight times more caffeine than a cup of coffee. Because herbal medications are not regulated by the FDA, labels regarding caffeine content are not required.
Significance
Caffeine affects the embryo and the fetus by crossing the placental barrier and entering the environment of the early embryo and later the bloodstream of the fetus.
Caffeine is a chemical that can affect various signaling pathways in the human body. Cyclic adenosine monophosphate, or cAMP, is a signaling molecule that is critical to growth and development. Caffeine indirectly increases cAMP by inhibiting phosphodiesterase, an enzyme that regulates cAMP. Animal studies suggest that an increase in cAMP can interfere with embryonic development.
Research
At extremely high doses used in animal studies, caffeine caused defects in embryonic development, fetal demise and low fetal weight, according to The Motherisk Program at The Hospital for Sick Children in Toronto, Canada, a clinical, research and teaching program devoted to promotion of healthy pregnancies. However, clinical human studies give conflicting results, depending on the dose of caffeine tested.
According to the National Toxicology Program, human clinical studies suggest that doses below 150 mg of caffeine, or about one and a half cups of coffee, per day are generally safe. Doses of more than 300 mg caffeine, or about three cups of coffee per day, or above have been associated with a greater risk of miscarriage. The effect of coffee on miscarriage can be increased if tobacco and alcohol also are used.
Considerations
The effects of caffeine can change during the time frame of the pregnancy because the clearance rate for caffeine changes.
During the first trimester, the mother clears caffeine from her system relatively quickly, with a half-life on average of between two and a half to four and a half hours. With the second and third trimester, the half-life of caffeine increases to as much as 10.5 hours and thus persists in the fetal environment.
When caffeine passes through the placenta, it enters the amniotic fluid and umbilical cord blood, where it can affect the fetus. Fetuses have relatively low levels of the enzymes needed to clear caffeine from the system.
Expert Insight
Both March of Dimes and Mothersafe advise pregnant women to reduce or eliminate the use of caffeine during their pregnancies even though low levels of coffee consumption probably are safe for most pregnant women.
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