Researchers are advising pregnant women to cut out coffee, tea and treats.
A link between pregnant women's caffeine consumption and excessive childhood weight gain has been found, prompting researchers to advise expectant mothers to avoid caffeine.
The study from the Norwegian Institute of Public Health looked at 50,000 mothers and children and found a link between children exposed to more than 200mg of caffeine per day (two coffees or four teas) and excess weight gain during early childhood.
It included caffeine consumption from coffee, tea, energy drinks, and sugary treats.
Existing guidelines in Australia and New Zealand recommend limiting caffeine intake while pregnant, but the Norwegian researchers are telling mothers to go cold turkey.
But the observational study did not provide a clear cause and effect. It found that those with a high caffeine intake were more likely to smoke, be less educated, have been obese before pregnancy and have partners who are obese and smokers.
Some experts are advising that the study should be viewed with caution.
Australian Medical Association spokesperson for obstetrics and gynaecology Dr Gino Pecoraro said the research "may provide further evidence that limiting caffeine intake during pregnancy may have beneficial effects for the developing child".
"While interesting and worthy of discussion with would-be and pregnant women, the exact level of safe caffeine consumption in pregnancy is not clear, although whether doctors should just advise total abstinence as in alcohol where the safe level is unclear, remains to be seen," Dr Pecoraro said.
Dr Clovis Palmet, Senior Monash University Fellow and Burnet Institute head of immunometabolism and inflammation, said: "The researchers provided no evidence of a causal link between prenatal exposure to caffeine and early childhood obesity. In this study, the mothers with high caffeine intake were most likely to be heavy smokers, economically disadvantaged, have poor diet and be overweight. These factors may have had stronger influence on early childhood obesity than dietary caffeine intake itself."
Dr Palmet said women are already encouraged to limit caffeine intake during pregnancy, and the study adds to a growing body of work supporting that advice.