Carried out by a team of Norwegian, Swedish and French researchers, the large-scale study looked at 50,943 Norwegian mother and infant pairs and asked the mothers to complete a questionnaire about their food and drink intake at 22 weeks of pregnancy.
Sources of caffeine on the questionnaire included coffee and black tea, which are the most common and major sources of caffeine, caffeinated soft/energy drinks, chocolate, chocolate milk, sandwich spreads, and desserts, cakes and sweets.
A daily intake of 0-49 mg was considered to be a low level of caffeine, with 50-199 mg considered average, 200-299 mg high, and more than 300mg very high.
46 percent of the women were classified as having a low caffeine intake, 44 percent had an average intake, 7 percent had a high intake, and 3 percent a very high intake.
The team also found that the higher the intake of caffeine, the more likely it was that the mother was older than 30, had had more than one child, consumed more daily calories and smoked during her pregnancy.
Women with a very high caffeine intake during their pregnancy were also more likely to be poorly educated and to have been obese before they got pregnant.
The team also measured the children’s weight, height and body length at 11 points between the ages of 6 weeks old and 8 years of age.
After taking into account potential influencing factors, the team found that an average intake of caffeine during pregnancy was associated with 15 percent increased risk of faster excess growth in childhood when compared to a low intake of caffeine.
This risk increased to 30 percent for a high intake of caffeine, and 66 percent for a very high intake.
Children exposed to very high levels of caffeine before birth also weighed 67-83 g more at 3-12 months, 110-136 g more as toddlers, 213-320 g more at 3-5 years, and 480 g more at the age of 8, than children who had been exposed to low levels.
Caffeine is the world’s most widely consumed central nervous system stimulant. It passes rapidly through the body’s tissues, including the placenta, but takes the body longer to get rid of during pregnancy. It has already been linked to a heightened risk of miscarriage and restricted fetal growth, with several authorities agreeing that caffeine intake should not exceed 200 mg/day during pregnancy.
As an observational study, the researchers cannot confirm causality, however, they did point out that the sample size was large, and the findings do support the existing advice to limit caffeine intake while pregnant.
“The results add supporting evidence for the current advice to reduce caffeine intake during pregnancy and indicate that complete avoidance might actually be advisable,” they added.
The results have been published online in the journal BMJ Open.