Giving birth by caesarean section may reduce levels of a molecule vital to brain development in newborn babies, a controversial study has suggested.
Scientists found that natural birth triggered production of the protein UCP2 in the brains of infant mice, while less of the protein was made in mice delivered by C-section.
UCP2, or mitochondrial uncoupling protein 2, is important for the proper development of brain circuits linked to memory, the researchers pointed out.
Blocking or knocking out the protein led to impaired brain function and behaviour in adult mice.
Other evidence suggested that induction of UCP2 by natural birth may help the transition to breast feeding.
A leading British expert warned against making the "large leap" of assuming women might harm their babies' brain development by having caesareans.
The research was carried out by a team of US scientists led by Professor Tamas Horvath, chair of the Department of Comparative Medicine at Yale University and their findings were published in the online journal Public Library of Science ONE.
Prof Horvath delivered a stark message to women who had C-section births out of choice rather than for medical reasons: "These results reveal a potentially critical role of UCP2 in the proper development of brain circuits and related behaviours. The increasing prevalence of C-sections driven by convenience rather than medical necessity may have a previously unsuspected lasting effect on brain development and function in humans as well."
But Professor Marian Knight, an honorary consultant in public health at Oxford University, was critical of the American research and said its findings should be viewed with caution.
"Whilst this is an interesting laboratory study, the potential for human significance is far from established," she said. "The authors speculate that there may be significance for human development, however, this paper does not establish whether the observed changes have long-term consequences for mice let alone humans, and it is a large leap to assume that this observed effect may have long-term consequences for babies."