Caffeine and Pregnancy
The March of Dimes notes that during pregnancy, caffeine easily passes from the mother to her unborn child through the placenta. Because the systems for breaking down and eliminating chemicals are not fully developed in the unborn child, blood levels of caffeine may remain elevated for longer periods in the unborn child compared to the mother. OTIS notes that, "…[H]igher amounts of caffeine could affect babies in the same way as it does adults. Some reports have stated that children born to mothers who consumed more than 500 mg/day were more likely to have faster heart rates, tremors, increased breathing rate, and spend more time awake in the days following birth."
The effects of caffeine intake on miscarriages, birth defects, and low birth weight have been studied, and different results were obtained in the various studies. The International Food Information Council (IFIC) has described and made conclusions about the following studies.
Recently, researchers from McGill University in Montreal, Canada, published a study showing a relationship between caffeine intake and miscarriage. While intake of this substance before and during pregnancy appeared to be associated with increased miscarriage, the authors failed to account for a number of factors that could result in a false association, including effects of morning sickness or nausea, the number of cigarettes smoked, and the amount of alcohol consumed.
Just prior to the McGill study, a research team from the National Institute of Child Health and Human Development in the United States conducted a study of 431 women. The researchers monitored the women and the amount of caffeine they consumed from conception to birth. After accounting for nausea, smoking, alcohol use, and maternal age, the researchers found no relationship between caffeine consumption of up to 300 mg per day and adverse pregnancy outcomes, including miscarriage.
Earlier, in 1992, researchers analyzed the effects of cigarettes, alcohol, and coffee consumption on pregnancy in more than 40,000 Canadian women. Although alcohol consumption and smoking tended to have adverse effects on pregnancy outcome, moderate caffeine consumption was not associated with low birth weight or miscarriages. Furthermore, the relationship of caffeine consumption to spontaneous abortion was investigated in a study of 5,342 pregnant women in 1997 in which researchers concluded that there was no increased risk for spontaneous abortion associated with moderate caffeine consumption. Another comprehensive study, done in Uppsala, Sweden, and reported in December 2000, concluded that reducing intake during the early stages of pregnancy may be wise.
Studies published during the 1980s also support the conclusion that moderate consumption during pregnancy does not cause early birth or low birth-weight babies. A review of more than 20 studies conducted since 1980 found no evidence that caffeine consumption at moderate levels has any discernible adverse effect on pregnancy outcome.
A seven-year study of 1,500 women examined caffeine use during pregnancy and subsequent child development. Caffeine consumption, equivalent to about 1½ to 2 cups of coffee per day, had no effect on birth weight, birth length, or head circumference. Follow-up examinations at ages eight months, four years, and seven years also revealed no effects of caffeine consumption on a child's motor development or intelligence.
In the early 1980s, the US Food and Drug Administration (FDA) conducted a study in which rats were force-fed high doses of caffeine through a stomach tube. While the results prompted an advisory to pregnant women to avoid caffeine, the study was criticized as not being representative of the way humans consume caffeine. In 1986, FDA researchers carried out another study in which rats consumed high doses of caffeine in their drinking water. At the conclusion of the second study, the FDA found no adverse effects in the offspring, contradicting the agency's earlier findings.
A recent study published in 2001 examined the effect of caffeine consumption on fetal growth and found no evidence that caffeine consumption during pregnancy has an adverse effect on fetal growth. In addition, a 2002 study found no association between moderate caffeine consumption and reduced birth weight, gestational age, or fetal growth.
Major studies over the last decade have shown no association between birth defects and caffeine consumption. The FDA has evaluated this scientific evidence and concluded that caffeine does not adversely affect reproduction in humans. However, as with other dietary habits, the agency continues to advise pregnant women to consume caffeine in moderation.