The research, published in the Maternal and Child Health Journal, followed more than 24,000 mothers and their children over 10 years and is the first to link excess weight and blood sugar control to an increased likelihood of childhood obesity even in babies who are normal weight at birth, say the team behind the work.
"When women have elevated blood sugar and gain excess weight during pregnancy, it seems to change the baby's metabolism to 'imprint' the baby for childhood obesity," said Dr Teresa Hillier, lead author and senior investigator with the Kaiser Permanente Center for Health Research. "We're not sure yet of the exact mechanism of this change, but it appears the baby is adapting to an overfed environment, whether from glucose or extra weight."
The Kaiser Permanente research team noted that although previous research has shown that excess weight and elevated blood sugar during pregnancy increase a woman's risk of delivering a large baby who is more likely to become an obese child; until now, there wasn't much evidence that these risk factors also affected normal-weight babies.
Hiller and her colleagues said the results show the effect in the womb on the baby's metabolism may be as important as what happens after the child is born – adding that further research should focus on pregnancy as a potential window of opportunity to reduce childhood obesity.
"We can't wait until the baby is born to determine and address the impact on childhood obesity," Hillier added. "We need to intervene during the mom's pregnancy to help her with nutritional and lifestyle changes that will result in healthy weight gain, healthy blood sugar and ultimately, healthy children."
The research team followed a study population of 24,141 individuals including mothers and their normal birth weight children born between 1995 and 2003. They found that all children of mothers who had elevated blood sugar during pregnancy were at higher risk for childhood obesity, but those whose mothers had gestational diabetes -- the highest level of elevated blood sugar -- were at the greatest increased risk.
Those children were at least 30% more likely to be overweight or obese between the ages of 2 and 10, compared to children whose mothers had normal blood sugar, said Hillier and her colleagues.
Furthermore, they reported that children of mothers who gained 40 pounds (18.1 kg) or more during pregnancy were at least 15% more likely to be overweight or obese between the ages of 2 and 10, compared to children whose mothers gained less than 40 pounds.
“These maternal glucose and/or weight gain effects to imprint for childhood obesity in the first decade remained after adjustment for potential confounders including maternal age, parity, as well as pre-pregnancy BMI,” the researchers wrote in their study.
Tam Fry, spokesperson for the UK-based National Obesity Forum said the research “demonstrates once again that failure properly to oversee pregnancy events can mean picking up the pieces for years to come.”
“It's a no brainer that prevention is better than cure yet we still seem to prefer waiting to see children get fat rather than trying to ensure that they never do,” he noted. “Why bother to fund researchers if no notice is paid to what they tell us?"
The study, which was completed by scientists at the Kaiser Permanente Center for Health Research was funded by a grant from the American Diabetes Association and the National Institute of Child Health and Human Development.