Mothers who give birth naturally are more responsive to the cry of their baby than those who choose to have a caesarean, American research suggests.
Brain scans on 12 new mothers soon after birth found more activity in areas linked to motivation and emotions in those who had a vaginal delivery.
The Yale University team says differences in the hormones generated by birth could be the key.
The contractions, which are an essential part of a natural birth, trigger the release of the hormone oxytocin, which is thought to play a key role in shaping maternal behaviour.
However, undergoing a caesarean does not trigger the same release of hormones.
The Yale team carried out brain scans on 12 women two to four weeks after they had given birth – known as the early postpartum period. Half had a caesarean, the other half gave birth naturally.
The differences in brain activity were found in regions that not only appeared to influence a mother’s response to her child, but also to regulate her mood.
Professor James Walker, a spokesman for the Royal College of Obstetricians and Gynaecologists, said: “We have long recognised that people who have a caesarean section do sometimes have some problems bonding with their baby.”
However, Professor Walker said the reason for this was unclear. In some instances, it might be related to clinical difficulties which made a caesarean necessary in the first place.
He said it was also possible that women who had a caesarean were slightly disengaged from the birth process in comparison to those who went through a natural delivery.
Professor Walker said there were no long-term studies assessing whether mothers who had a caesarean had longer-term problems bonding with their baby.
“There is no doubt that many women who have a caesarean turn out to be wonderful mothers,” he said.
Belinda Phipps, of the National Childbirth Trust, said: “Bonding between a mother and baby is highly important and responding to a new baby’s cry is a key part of maternal attachment.
“Women who have a caesarean section should be encouraged to cuddle their newborn against their skin straight after birth and be offered practical support to help them feed and care for their baby.”
Between 10% and 20% of all births in the UK are now delivered by caesarean.