April 24 (UPI) -- A child's excess weight gain has been linked to at least moderate caffeine levels while in the womb, according to a study in Norway.
Researchers wanted to find out if moderate to high caffeine intake during pregnancy might be associated with excess weight gain in children's early years. The findings were published this week in the journal BMJ open.
Pregnant women have previously been advised to limit caffeine intake, but the researchers now wonder whether to totally cut the stimulant out.
"Any caffeine consumption during pregnancy is associated with a higher risk of excess infant growth and of childhood overweight, mainly at preschool ages," the researchers wrote in the study. "Maternal caffeine intake may modify the overall weight growth trajectory of the child from birth to 8 years. This study adds supporting evidence for the current advice to reduce caffeine intake during pregnancy."
The study examined 50,943 women from across Norway who took part in the Norwegian Mother and Child Cohort Study between 1999 and 2008.
The consumption of food and drink intake from among 255 items, including caffeine, was reported at 22 weeks during pregnancy and the children's growth patterns were tracked starting at 6 weeks old; then at 3, 6, 8 and 12 months; and then at 1-1/2, 2, 3, 5, 7 and 8 years of age.
Sources of dietary caffeine can include coffee, black tea, caffeinated soft/energy drinks, chocolate, chocolate milk, sandwich spreads; and desserts, cakes and sweets.
The mothers to be were grouped into four categories based on daily intake: 0-49 mg was low, 50-199 mg was average, 200-299 mg was high and 300 mg and above was very high.
An 8-ounce cup of caffeinated coffee typically has between 100 and 150 milligrams of caffeine, and an 8-ounce cup of black tea or cola between 25 and 50 milligrams of caffeine, according to the Mayo Clinic.
World Health Organization criteria was used for excess weight gain, and overweight and obesity were assessed based on International Obesity Task Force criteria.
Of the participants, 46 percent were classified as low caffeine intake, 44 percent as average, 7 percent as high and 3 percent as very high. The heightened risk for obesity was found to be 15 percent for average intake, 30 percent for high and 66 percent for very high.
The researchers found that exposure to any caffeine level while in the womb was linked to a heightened risk of overweight at the ages of 3 and 5 years. For 8-year-olds, it was among mothers who had a very high caffeine intake during their pregnancy.
On average, children exposed to very high levels of caffeine before birth weighed 2.4 to 2.9 ounces more at 3-12 months, 3.9 to 4.8 ounces more as toddlers up to 2, 5.7 to 11.2 ounces more as pre-schoolers from 3-5 years and 16.9 ounces more at the age of 8 compared with children who weren't exposed to these levels.
Researchers found higher caffeine levels linked to mothers older than 30, who had more than one child, consumed more daily calories and smoked during pregnancy. Also, women with a very high caffeine intake during their pregnancies were more likely to be poorly educated and obese before they got pregnant.
Although the study is the largest on the association of prenatal caffeine exposure and childhood growth parameters, the researchers wrote that "our findings might be explained by residual confounding of non-accounted factors related to an overall unhealthy lifestyle and high caffeine consumption; though exclusion of smokers and very high caffeine consumers did not modify the results."
Other studies have confirmed problems with caffeine intake during pregnancy, including a 2015 study by Kaiser Foundation Research Institute that found exposure to caffeine in the womb was associated with an 87 percent increased risk of childhood obesity.
A 2008 study conducted by Kaiser Permanente also found that women who consumed more than 200 milligrams of caffeine per day were more than twice as likely to have a miscarriage than non-caffeine consumers.