Caffeine During Pregnancy Nearly Doubles Childhood Obesity Risk

Mothers were questioned on a regular basis during their pregnancy about their diet and caffeine intake, and then health records of their children were examined. Jorge Silva / REUTERS

Should pregnant women avoid caffeine?

Recent research suggests that they might want to at least consider giving up coffee for those nine months. A study published last month in the International Journal of Obesity found that children born to mothers who drank caffeine-laden drinks during pregnancy were 89 percent more likely to be obese, compared to kids of moms who abstained.

And the more one drinks, the higher the risk, says study author Dr. De-Kun Li, a physician and researcher at Kaiser Foundation Research Institute and Stanford's school of medicine. Children born to mothers who consumed more than 150 milligrams of caffeine daily, equivalent to a medium-sized cup of coffee, were 2.3 times more likely to become obese.

The study followed more than 600 mothers and children over a 15-year period. Moms were questioned on a regular basis during their pregnancy about their diet and caffeine intake, and then health records of their children were examined.

Caffeine easily passes the placental barrier between the mother's and fetus's blood, Li's previous work has shown. But it's not known exactly how the substance affects the developing fetus. Animal studies show that caffeine can interfere with the ability to metabolize sugar. The chemical also increases insulin resistance, which can lead to higher blood sugar levels. Caffeine also affects the development of the hypothalamic–pituitary–adrenal axis, the part of the brain involved in metabolism, Li says.

The study controlled for a slew of confounding factors that might play a role in obesity, including the mother's age and body mass index (BMI), whether or not the child was breastfed, the family's socioeconomic status and other measures.

Childhood obesity is an increasingly vexing problem; In the past 30 years, it has doubled in children and quadrupled in adolescents, according to the Centers for Disease Control and Prevention. And in 2012, more than one third of children and adolescents were overweight or obese.

Caffeine consumption during pregnancy has long been a concern due to possible effects including premature birth and miscarriage, says Leonardo Trasande, a researcher at NYU's school of medicine who wasn't involved in the paper. Trasande says that this study is well-done and suggests that caffeine may be a risk factor for obesity. But, he adds, it also doesn't rule out the possibility that there may be other contributors like childhood diet.

That said, the American College of Obstetricians and Gynecologists has in the past reviewed the scientific literature and suggests that moderate caffeine consumption does not contribute to miscarriage or preterm birth. "Further study is needed before doctors should consider changing this advisory, to consider [adding] other risks such as obesity," Trasande says. Even still, he suggests that "pregnant women should limit their consumption of caffeine" in the meantime.

Michele La Merrill, a toxicologist at the University of California-Davis who wasn't involved in the study, says that "when risk is less than doubled by something, as it is with caffeine here, it is generally not considered a big risk." However, she adds, "given how commonly caffeine is used during pregnancy even a small risk associated with its use could affect many people."

She noted that caffeine consumption has been linked with having smaller babies. And being small at birth actually increases risk for obesity later in life. For this reason, she says she believes "it is wise for pregnant women to consider reducing or eliminating their caffeine use."