A team at the Boston Children's Hospital in Massachusetts looked more than 1,250 pairs of mothers and children from 1999 to 2002 and found that children born by C-section had double the odds of obesity by the time they become three years.
After taking into account obesity in the mother and other factors, they found almost 16 per cent of children delivered by Caesarean were obese by the age of three compared with 7.5 per cent born naturally, the BBC News reported.
The team said birth by C-section might affect bacteria in the gut, which in turn affects the way food is digested.
In the study, published in journal Archives of Disease in Childhood, the researchers measured the weight of babies at birth and after they reached three years. They found a link between body mass, skin thickness and how a child was born.
They also found that mothers who delivered by C-section tended to weigh more than those delivering traditionally -- something which is known to influence obesity.
But the researchers said another possible explanation was the difference in the composition of gut bacteria acquired at birth between the two delivery methods.
They suggested expectant mothers who choose a C-section should be made aware of the obesity risk to their babies.
Patrick O'Brien, a spokesman for the Royal College of Obstetricians and Gynaecologists, said: "This is an interesting study, but small. It needs to be replicated in a bigger sample."
