New research has found a link between elective caesareans and the risk of babies being overweight by the time they turn one.
Researchers believe babies don't experience the stress of labour during c-sections, and aren't exposed to their mother's bacteria.
The international research also found a difference in outcome when comparing emergency and elective c-sections.
University of Auckland's Liggins Institute examined data from more than 700 babies and their mothers in Singapore.
In NZ, around a quarter of all births are caesarean, with more than two-thirds of those elective caesareans, Stuff reported last year.
Child obesity expert Professor Sir Peter Gluckman, who helped with the research, said a hormone surge during natural birth could help put the child on the right path, weight-wise.
He said there was a 'rising epidemic' in elective c-sections.
"This study waves a flag - this is a social trend rather than a health trend - and it is not without some potential costs for the baby," he told Stuff.
He said if there were medical reasons for a c-section, he fully advocated the procedure.