Even a Little Caffeine While Pregnant Could Increase Child's Obesity Risk: Study

Ingesting caffeine, such as by drinking coffee, while pregnant could increase the risk of having an overweight child. Three Lions/Getty Images

Pregnant women who drink coffee or even eat foods with low levels of caffeine might give birth to babies who are at a higher risk of becoming overweight, according to new research.

A study in the journal BMJ Open found an association between even an average portion of caffeine and infant weight growth. And caffeine ingested at any level was reportedly connected to a greater risk of the child being overweight throughout the first several years of life.

Doctors already advise expectant mothers to limit how much caffeine they consume, and the study provides further backing for that recommendation. However, it speaks to a trend and not to causality because it was observational in nature.

"Caffeine passes rapidly through tissues, including the placenta, and takes the body longer to get rid of during pregnancy," the British Medical Journal explained. "It has been linked to a heightened risk of miscarriage and restricted fetal growth."

The new research was based on information from almost 51,000 mothers who reported their caffeine intake through items such as coffee, tea, soft drinks, chocolate or chocolate milk and desserts like cake. That was compared to data collected on the offspring's weight and height at 6 weeks, 3 months, 6 months, 8 months, 12 months, 18 months, 2 years, 3 years, 5 years, 7 years and 8 years old.

Women who ingested less than 50 milligrams of caffeine on a daily basis, the low-intake group, were the only ones who didn't see their children go through "excess growth in infancy," according to the study.

Fifty milligrams of caffeine equates to about half of a standard 8-ounce cup of coffee, according to U.S. Department of Agriculture guidelines.

But all the groups of women taking in any caffeine whatsoever—from low intake through average, high and very high intake—were found to have children at a greater risk of being overweight at ages 3 and 5.

Mothers who ingested a lot of caffeine saw a continued heightened risk through when the child was 8 years old—those kids were about 1 pound heavier than their counterparts.

The researchers focused on how in utero exposure to caffeine potentially affected weight because "fetal growth and growth in infancy are important determinants for the development of obesity and for long-term cardiometabolic health."

Almost half of the pregnant subjects were classified as being "low intake," and almost another half qualified for the average intake group. Only 3 percent of the women had a very high intake and about 7 percent had a high one.

"Caffeine is the world's most widely consumed central nervous system stimulant," the researchers said in their study.

Although the general recommendation for caffeine intake while pregnant is that it should be limited to less than 200 milligrams a day, the equivalent of about two cups of coffee, this study would group those mothers into low or average intake—groups that also saw an effect on their child's weight.