Drinking half a cup of coffee per day while pregnant may increase the risk that a baby has a lower birth weight and size, according to the new findings of a new study that raise concern about the side effects of caffeine consumption during pregnancy.
In a report published last month in the medical journal JAMA Network Open, researchers indicate that infants born to mothers who drank more than half a cup of coffee a day had lower birth weight, smaller heads and overall smaller birth size, which may be signals for potential health risks.
The National Institute of Child Health and Human Development Fetal Growth Studies-Singletons cohort study focused on more than 2,000 women treated at 12 clinical sites from 2009 to 2013. Researchers from the institute measured caffeine consumption using both blood draws and self-reported consumption reported at 10 to 13 weeks pregnancy.
Mothers who had the highest levels of caffeine, above 659 ng/mL, had a higher risk of giving birth to smaller infants who had lower birth weight, lower birth length, smaller head size, and smaller thigh circumference when compared to those who had the lowest levels; below 28 ng/mL. The more caffeine a mother had, the higher the risk her child was born smaller, which can lead to negative health effects later in life.
Compared with women who reported drinking no beverages containing caffeine, women who consumed 50 mg of caffeine per day, the equivalent of 1/2 cup of coffee, gave birth to infants with lower birth weight and smaller arm and thigh circumference.
The research indicates caffeine consumption, even in amounts less than the recommended 200 mg per day, is linked with smaller birth weight and size.
Prior studies have also linked high caffeine consumption, more than 200 mg per day, with lower birth weight. This led health experts to recommend consumption below 200 mg per day, or no more than roughly 2 cups of coffee per day.
Researchers speculate caffeine can cause blood vessels in the uterus and placenta to constrict, which can reduce the blood supply to the fetus and inhibit the growth of the infant. Caffeine can also potentially disrupt fetal stress hormones. This increases an infant’s risk for rapid weight gain after birth and increases the risk the infant will be obese later in life. They may also suffer from heart disease and diabetes.
“In this cohort study, small reductions in neonatal anthropometric measurements with increasing caffeine consumption were observed,” the researchers concluded. “Findings suggest that caffeine consumption during pregnancy, even at levels much lower than the recommended 200 mg per day of caffeine, are associated with decreased fetal growth.”
The study did not prove cause and effect and had limiting factors. It did not account for other factors that could influence infant birth weight or size, such as maternal smoking habits.
Researchers recommend limiting or eliminating caffeine intake during pregnancy to avoid side effects linked to caffeine intake. They also recommend pregnant women talk to their doctors about caffeine consumption during pregnancy to determine the best options for them.