As the prevalence of Caesarean section births continues to increase in the United States, new research from the Yale School of Medicine suggests that the procedure may impair brain development in offspring.
A team of researchers led by School of Medicine Professor Tamas Horvath found that newborn mice birthed naturally had increased levels of mitochondrial uncoupling protein 2 (Ucp2) in the hippocampus relative to mice delivered through C-sections. Horvath said the team was initially focused solely on the role of Ucp2, an important protein for early neurological development, and was surprised to discover a link between levels of Ucp2 and birthing methods. The study, which also concluded that mice genetically altered to lack Ucp2 exhibited greatly diminished neurological growth, was published Aug. 8 in the Public Library of Science.
“What we noticed what that if we took brains right after birth versus if we took brains from animals right before they were delivered, there were differential expression of these proteins,” Horvath said. “[We thought]: ‘Maybe there is something going on during delivery that promotes the expression of this protein.’”
The study did not investigate the mechanism underlying the correlation between natural birth and increased Ucp2 expression, but Horvath said that he believes that the physical stress of natural birth may explain the connection. Researchers had previously tied cellular stress to Ucp2 production, and the stress of natural birth — both for the mother and child — might trigger the protein’s production, Horvath said.
Holly Kennedy, a professor of midwifery at the Yale School of Nursing who was not involved in the research, said the finding is important because it counters the common misperception that the stress of natural birth is harmful.
“I think what people worry about is that labor and birth is so stressful that it can’t be good for the mother or the baby,” she said. “Well, there are types of stress that are good and actually create health.”
Professor Horvath said that he believed that physiological cellular stress, likely caused by temporary fetal oxygen depletion, was the primary mechanism for Ucp2 production in babies. However, Grigori Brekhman, former head of the Department of Obstetrics and Gynaecology at the Ivanovo State Medical Academy, in the Russian Federation, said in an email that other factors may be involved in the protein’s production. For instance, Brekhman said that the mother’s emotional response to the birthing process, accompanied by a cascade of neurological transmitters, may promote Ucp2 production.
This study substantiates the argument of those who had already supported natural births, said Ann Cowlin, founder and director of Dancing Thru Pregnancy, an organization that helps pregnant women prepare for the physical demands of childbirth. Cowlin, who created Dancing Thru Pregnancy in 1979, said that she would rank Horvath’s finding as one of the top five most important pieces of evidence in the debate between natural birth and C-section.
“This is the smoking gun to end the whole notion that it is a good thing to just go ahead and do a Caesarean and not even bother to do labor,” Cowlin said.
While Brekhman said that he believes the findings will encourage more women to reconsider C-sections in favor of traditional births, Kennedy said that Horvath’s finding is unlikely to cause a major short run shift in birthing practices because it was conduced on mice and not humans. However, it adds to a growing body of recent research that suggests that the way a baby is born can have long lasting health implications for the newborn, she said.
“I think what it is providing us is food for thought about this process and a call for more research,” Kennedy said.
Horvath, too, said that he hopes that others build on his findings with a human study which could lead to concrete data on best practices for birthing.
While the World Health Organization recommends a target C-section rate of 5 to 15 percent in the general population, the operation accounts for approximately one in three births in the United States today.