A protein critical for brain development and function is triggered when babies are delivered through natural birth but not when they're born via C-section, according to researchers at Yale.

UCP2 (mitochondrial uncoupling protein 2) is important for the development of neurons and circuits in the hippocampus -- the area of the brain responsible for short- and long-term memory.

When Prof. Tamas Horvath and his team studied natural and surgical deliveries in mice, they found significantly higher levels of UCP2 in mice born via vaginal birth compared with those born by C-section.

What's more, UCP2 levels remained elevated in adulthood in the naturally born mice, the team found.

Diminished levels of the protein could have long-lasting effects, the authors said. In behavioural tests they found that the surgically born mice were slower-moving, stuck close to the walls of their enclosure and didn't venture very far.

The implications of the research could affect a woman's choice to deliver by C-section -- when there is a choice.

"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," Horvath said.

The findings are published in the August issue of the scientific journal PLoS ONE.