The findings, published in the US journal PLoS Medicine, suggested pregnancy may be "an especially important time" to prevent obesity in the next generation, Xinhua reported.
Researchers from Boston Children's Hospital looked at 41,133 mothers with two or more children to find out whether childhood obesity was resultant because of the conditions during pregnancy or other factors, such as diet and genes, also played a role.
They linked the birth records of mothers with two or more children to school records that included the child's body mass index (BMI) at an average age of 11.9 years, and then made statistical comparisons between siblings.
The researchers feel comparing siblings minimises the conventional sources of confounding, because on average siblings have the same relative distribution of obesity genes, the same home environment and same socioeconomic and demographic influences.
The study showed that for each kilogramme of weight gain during pregnancy, the body mass index of a child at age 12 increased by 0. 02 kg per square metre.
"Excessive pregnancy weight gain may make a significant contribution to the obesity epidemic," senior author David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital, said in a statement.
The researchers, however, noted that additional research was needed to learn how best to advise pregnant women on managing their weight in pregnancy.