Experts generally agree that most healthy, risk-free women should deliver their babies vaginally rather than by cesarean section, as it has benefits for both the mother and baby, like shorter hospital stays and fewer infant respiratory problems.
Now, Yale researchers said they've found another potential benefit of vaginal birth, claiming it triggers the production of a protein in babies' brains that may improve brain development.
Giving birth via c-section, on the other hand, may impair its expression.
"We were looking at the protein, and we realized that if you take a 'normal birth' mouse and compare it to a 'c-section mouse,' there are very different levels in the hippocampus," Tamas Horvath, a professor of biomedical research and chair at the department of comparative medicine at the Yale School of Medicine, told The Huffington Post. The findings were published in the online research journal PLoS One, Wednesday.
The "uncoupling 2 protein," or UCP2, is important to the development of the circuitry in the hippocampus, which helps with the formation and storage of memory. Development, he said, was "very important for behavior in the long run."
But because the research was done in mice, it is highly preliminary. The research also looked at vaginal birth broadly, not at whether anesthesia use could influence protein production.
Researchers do not yet know why different delivery modes influence the protein, although Horvath guessed that the pressure and stress of traveling the birth canal may trigger it.
Other recent studies on the impact of different birthing methods have focused on immune system function.
A 2010 study in the journal PNAS suggested that as babies travel through the vagina during birth, they may pick up certain bacteria that could help protect them from future diseases. But that research is also still preliminary.
The new study is among the first to look at how natural and surgical deliveries might boost or impair brain development, Horvath said.
But he called the questions it raises about the effect of vaginal and c-section births "intriguing," and said he hoped future studies would go on to look at whether it matters if labor is induced, or anesthesia is used.
“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 in a statement released by Yale.
C-sections are typically performed when unexpected problems arise during delivery, such as signs of fetal distress that require a faster birth, although "public health experts think that many c-sections are unnecessary," the U.S Department of Health and Human Services warns.
In 2010, the most recent year for which the Centers for Disease Control and Prevention has data available, c-sections were performed in 32.8 percent of all births in the U.S.