Though recent data has shown that childhood obesity numbers are falling in a number of U.S. states, health officials in the country are still referring to obesity as an epidemic. This week, a new study has shown that expectant mothers may have more direct, biological influence on the size of their children than previously thought.

The study, published Monday in the journal PLoS Medicine, shows that high weight gain during pregnancy is directly linked to an increased risk of obesity for the children up until age 12. The study’s authors believe that helping women limit their weight gain during pregnancy could have an impact on the fight against obesity in the U.S.

“From the public health perspective, excessive weight gain during pregnancy may have a potentially significant influence on propagation of the obesity epidemic,” said Dr. David Ludwig, lead author of the study and the director of the Boston Children’s Hospital’s Obesity Prevention Center. “Pregnancy presents an attractive target for obesity prevention programs, because women tend to be particularly motivated to change behavior during this time,”

The study looked at 41,133 mothers and children in the state of Arkansas over 12 years, cross-referencing birth records and school BMI records. Statistical comparisons were then made between siblings, ruling out demographic, genetic, and environmental influences. Excessive weight gain in the study was defines as 40 or more pounds, which correlated to an 8% increase in the risk of a child being obese.

Though the difference in BMI from mothers who gained the least weight during pregnancy to those who gained the most is only one-half of a BMI unit, Ludwig and his colleagues believe this effect could contribute to hundreds of thousands of obesity cases nationwide.