Natural birth could lead to better bonding with the child. For such mothers tend to be more responsive to the cry of their baby than those who have a Caesarean, a Yale University study says.
Differences in the hormones generated by birth could be the key, the research team thinks.
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 contractions which are an essential part of a natural birth trigger the release of the hormone oxytocin, which is supposed to play a key role in shaping maternal behaviour.
In contrast, similar hormone-triggering does not seem to occur in women undergoing Caesarean.
The procedure has been linked to an increased risk of post-natal depression.
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.
Lead researcher Dr James Swain said the study, reported in the Journal of Child Psychology and Psychiatry, might help provide a better understanding of the chemistry underpinning the attachment between a mother and her baby.
"Our results support the theory that variations in delivery conditions such as with caesarean section, which alters the neurohormonal experiences of childbirth, might decrease the responsiveness of the human maternal brain in the early postpartum."