Exposure to any caffeine level while in the womb was associated with a heightened risk of overweight at the ages of three and five years, although this persisted only for those eight-year-olds whose mums had had a "very high" caffeine intake during their pregnancy.
"Average", "high", and "very high" caffeine intake during pregnancy were associated with a heightened risk - 15%, 30%, and 66%, respectively - of faster excess growth during their child's infancy than low intake, after taking account of potentially influential factors.
Researchers found mothers's caffeine consumption could lead to their children becoming overweight in later years.
But the observational study did not provide a clear cause and effect.
"In this study, the mothers with high caffeine intake were most likely to be heavy smokers, economically disadvantaged, have poor diet and be overweight".
Some experts are advising that the study should be viewed with caution.
Very high levels of caffeine consumption during pregnancy were linked with less than a pound of excess weight up to age 5, but slightly over a pound by age 8, the researchers reported. The researchers divided the intake into low (less than 49 mg), average (50-199), high (200-299), and very high (more than 300).
"Maternal caffeine intake may modify the overall weight growth trajectory of the child from birth to 8 years", the write.More news: YouTube Kids adding human curated channel collections, more parental restrictions
Study authors said their findings supported the recommendation that pregnant moms should reduce their caffeine intake to less than 200 milligrams a day, or below two cups of coffee.
Sources of dietary caffeine can include coffee, black tea, caffeinated soft/energy drinks, chocolate, chocolate milk, sandwich spreads; and desserts, cakes and candies. It passes rapidly through the body's tissues, including the placenta, but takes the body longer to get rid of during 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.
"Women must note that coffee and tea aren't the only source of caffeine, as it's often present in chocolates, sodas and some pain relief medicines".
"The evidence provided in the study for a causal effect is extremely weak and the statement from the authors that "complete avoidance might actually be advisable" seems unjustified, particularly when we consider the effects that such a restriction might have on wellbeing of mothers".
Around half (46 per cent) of pregnant women were considered to have low caffeine consumption - less than 50mg a day; A further 44 per cent had a moderate level of consumption - classed as between 50 and 199mg a day; 7 per cent had high levels of consumption of between 200mg and 299mg a day and 3 per cent had very high levels of over 300mg.
The report was published online April 23 in the journal BMJ Open. However, this study was not able to determine whether the increase in growth rate in the first year of life was due to an increase in bone and muscle mass, which tends to occur earlier, or body fat which occurs later.