Caffeine in pregnancy can reduce birthweight

Consumption of caffeine, whether from tea, coffee, chocolate or caffeinated drinks, increases the risk of giving birth to a low birth weight baby, according to the results of a study published Nov. 3 in BMJ Online First.

Justin C. Konje, MD, of the University of Leicester in the United Kingdom, and colleagues conducted a study of 2,635 low-risk pregnant women with an average age of 30 whose consumption of caffeine was assessed throughout their pregnancy. The patients' caffeine metabolism was also calculated using saliva tests.

Women who consumed 100 to 199 mg of caffeine per day were 20% more likely to have restricted fetal growth than those who consumed less than 100 mg a day, the equivalent of less than a cup of coffee, the authors discovered. The effect was greater for high caffeine intake, with a 50% higher risk for women who consumed 200 to 299 mg per day, and 40% for those who took over 300 mg per day, the study showed. There was a stronger association among women with faster caffeine clearance, the researchers found.

“We suggest that sensible advice for women contemplating pregnancy is to reduce their caffeine intake from all sources before conception,” the authors write. “Once pregnancy is confirmed, they should make every effort to stop or markedly reduce caffeine consumption.”

CARE Study Group. Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. BMJ. 2008;337:a2332. doi:10.1136/bmj.a2332.