The odds of being overweight or obese are 26% higher for adults born by caesarean section than for those born by vaginal delivery.
The finding is based on analysis of 15 studies involving over 38,000 individuals.
Effects of a surgery-assisted birth on a baby’s gut bacteria and genes could be a reason why babies born by C-section are more likely to be overweight or obese later in life.
Researchers at Imperial College in London said while there were good reasons why women should have a C-section, they should be aware that their might be long-term consequences for their children.
The rate of C-sections performed in some hospitals in Ireland is more than double the World Health Organisation’s recommended rate.
Figures recently published by the HSE show that most hospitals fall between the 25% and 30% bracket.
The new study, which includes data from 10 countries found that the average body mass index (BMI) of adults born by caesarean section is around half a unit more than those born by vaginal delivery.
Published in the journal, PLOS ONE, it is the largest to show a link between caesarean delivery and BMI in adulthood.
“This study shows that babies born by C-section are more likely to be overweight or obese later in life. We now need to determine whether this is the result of the C-section, or if other reasons explain the association,” said the report’s senior author, Neena Modi.
One of the researchers, Matthew Hyde, said there were plausible mechanisms by which caesarean delivery might influence later body weight.
“The types of healthy bacteria in the gut differ in babies born by caesarean and vaginal delivery, which can have broad effects on health.
“Also, the compression of the baby during vaginal birth appears to influence which genes are switched on, and this could have a long-term effect on metabolism,” he said.
Co-chair of the Association for Improvements in the Maternity Services, Ireland, Jene Kelly, said C-section rates were higher for women with higher BMIs and there was a direct link with a mother’s obesity and her child’s obesity.
Also, women who had a C-section tended to have lower breastfeeding rates and breastfeeding was linked to lower risks for obesity.
Ms Kelly said in Ireland, women with a BMI over 30 are considered high risk and that makes them only eligible for obstetric-led care options that have been shown to have higher rates of C-section.
“AIMS Ireland is concerned that C-sections may be used inappropriately, where there is no medical need or where the need for a caesarean has been created due to intentions prior to that point,” she said.