Pregnant women with obesity could reduce the health risks for their infants through improved diet and more physical activity, say researchers.

The study, published in the journal PLOS Medicine, investigated the impact of high glucose in mothers with gestational diabetes mellitus (GDM) and changes to infants DNA. GDM is becoming more frequent around the world alongside a rise in obesity and can increase the risk of complications during pregnancy and childbirth as well as increasing the risk of metabolic disease in the child in later life. High levels of glucose in mothers with GDM have been suggested to trigger epigenetic changes in the developing fetus (chemical modifications to the genetic blueprint of the fetus that function of genes activity) resulting in adverse health outcomes for the child. "These findings suggest that improvements to diet and physical activity can have an impact on the development of their children," said study author Karen Lillycrop from the University of Southampton in the UK.

For the study, the research team studied data from over 550 pregnant women with obesity and their children. The trial aims to improve the diet and physical activity of obese pregnant women across the UK. Compared to women in a control group, who made no changes to their lifestyle during pregnancy, women who were supported in changing their diet to lower glycaemic index foods that are broken down less quickly by the body, a reduced-fat intake and increasing their physical activity put on less weight and were metabolically healthier.

The researchers compared the level and pattern of DNA methylation, a major epigenetic mechanism which controls gene activity, in the new-born infants from mothers who developed GDM with those that did not. They then looked at whether a dietary and physical activity intervention during pregnancy altered these modifications in infants born to mothers who developed GDM. The results showed that GDM and high glucose levels in mothers were linked to changes in the level and pattern of functional modification to the infant's DNA. Moreover, they found that the dietary and exercise intervention significantly reduced these methylation changes in the infant associated with GDM in the mothers. "We have known for some time that children of mothers who had gestational diabetes are a greater risk of obesity and poor control of glucose; this new research implies that epigenetic pathways could be involved," the study authors wrote.