A recent study in BMJ Open shows that mothers exposed to moderate to high levels of caffeine during pregnancy may give birth to infants that gain excess weight in early childhood. The findings from the large observational study reinforce prior recommendations to limit caffeine intake during pregnancy to less than 200 mg per day.
The Norwegian study, which included 50943 mother-child pairs recruited from 2002 to 2008, recorded mothers’ caffeine intake during pregnancy and tracked their children’s growth at 11 age points from 6 weeks to 8 years. At 22 weeks of pregnancy, the expectant mothers were given an adapted 225-question Food Frequency Questionnaire, which included questions about daily caffeine intake and the sources of the caffeine (coffee, black tea, soft drinks, energy drinks, etc.).
The researchers categorized the mothers’ caffeine intake as low (0-49 mg/day), average (50-100 mg/day), high (200-299 mg/day), and very high (> 300 mg/day). The 11 age points at which the children’s weight and length were measured were 6 weeks; 3, 6 and 8 months; and 1, 1.5, 2, 3, 5, 7, and 8 years. Excess infant weight gain was assessed by calculating the difference in gender-adjusted World Health Organization weight-for-age z-scores between birth and 1 year. A z-score > 0.67 represents excess growth.
In the study population, 7.13% (n=3633) and 3.21% (n=1634) of women reported caffeine intake higher than 200 mg/day and 300 mg/day, respectively. The higher the caffeine intake, the higher the likelihood that a mother was older than age 30, multiparous, had a daily energy intake in the upper tertile, smoked during pregnancy, and did not suffer nausea and/or vomiting during pregnancy.
The prevalence of excess growth in infancy also increased from 23% to 29% as prenatal caffeine intake increased from low to very high. After adjusting for confounders, the researchers found that, compared to children born to women who were low consumers of caffeine, those born to women who consumed average, high, and very high amounts of caffeine had progressively higher odds of excess growth: 1.15 (95% CI: 1.09 – 1.22), 1.30 (95% CI: 1.16 – 1.45), and 1.66 (95% CI: 1.42 – 1.93), respectively.
As the participating infants aged, rates of overweight increased by 5% at age 3 years, 6% at age 5 years, and 3% at age 8 years in association with caffeine exposure from low to high to very high, respectively. Children born to average, high, and very high consumers of caffeine had adjusted odds for being overweight at age 3 years of 1.05 (95% CI: 0.99 – 1.12), 1.17 (95% CI: 1.05 – 1.30) and 1.44 (95% CI: 1.24 – 1.67), respectively. Children prenatally exposed to very high rates of caffeine weighed 67 to 83 g more in infancy (age 3-12 months), 110 to 136 g more in toddlerhood (age 1-3 years), 213 to 320 g more at preschool age (3-5 years), and 480 g more at 8 years than did children who were prenatally exposed to low caffeine levels.
The researchers noted that findings from this study reinforce those from previous studies on the associations between prenatal caffeine exposure and birthweight. However, this study also tracked weight gain velocities after birth, following the participating children for 8 years. Some of the strengths of the study were the large number of participants, frequency of the measurements, and assessment of caffeine intake from different sources. Identified weaknesses include the self-reported diet from the mothers and the inability to establish causation because the study was observational.