Study indicates vaginal births but not C-sections trigger brain-protecting proteins in babies

by faithgibson on March 2, 2013

in Contemporary Childbirth Politics


Some experts say that changing demographics – older first-time mothers, more twin births from fertility treatments, more mothers with hypertension, diabetes, obesity and other health problems – are not enough to explain an almost doubling in the C-section rate since the early 1990s.

The popularity of C-sections may carry a new and unsuspected risk.

A team of scientists led by the Yale University School of Medicine is reporting that natural or vaginal births, but not caesarean sections, appear to trigger the brains of newborns to release a protein critical for the survival and development of neurons and connections in the hippocampus — the brain region involved in learning and memory that shrinks with age.

In studies in mice, the team found significantly higher levels of the protein, known as UCP2, at the day of delivery in mice that were born via a vaginal birth than they found in those delivered by C-section.

And, in naturally born mice, the protein remained elevated in adulthood.

The researchers haven’t proven their findings in people. But they say it may give women and doctors who choose C-sections when there’s no medical need one reason to pause.

Some experts say that changing demographics – older first-time mothers, more twin births from fertility treatments, more mothers withhypertensiondiabetesobesity and other health problems – are not enough to explain an almost doubling in the C-section rate since the early 1990s.

Some women are requesting C-sections because of fear and anxiety over labour and delivery. But the wider concern is that too many are being ordered because labour isn’t progressing quickly enough.

“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,” lead author Tamas Horvath, professor of biomedical research and chair of the section of comparative medicine at Yale, said in a statement released with the study.

“I’m not saying, (one is) better or worse,” Horvath said in an interview.

“We don’t conclude anything clinical, but suggest that perhaps natural birth has a role of its own in inducing processes in the brain that are important for development and later function.”

The study is published this week in the journal PLoS ONE.

In Canada, about one in four women gives birth by caesarean, and the rate increases with age. For first-time mothers aged 40 and over, one in two delivers via a surgical birth, according to the Canadian Institute for Health Information.

Horvath’s team had been studying the protein’s role in brain function when they discovered by accident that mouse pups born naturally expressed higher levels of the protein than mice born by caesarean.

UCP2, which is found in a variety of tissues in the body, is a stress signal. “When you insult, or deprive cells of oxygen, the system gets activated,” Horvath said. The protein protects brain cells from damage.

During a vaginal birth, the sheer process of squeezing through a small birth canal places stress on the baby. “You have both physical pressure, you probably have hypoxia (low oxygen levels) associated with the process. And this is a natural reaction of that, to express this protein,” Horvath said.

“But it also seems that it plays an important role in overall development of brain tissue.”

To find out how mice lacking the protein behaved in adulthood, the researchers put mice in which the gene for UCP2 had been “knocked out” or inactivated through tests measuring hippocampal function.

In an “open field” test that measures how mice react to a new environment, the knockout mice were more anxious. They spent less time exploring the centre of the square arena, and more time hovering along the walls.

When the animals were put through a maze measuring spatial memory, mice lacking UCP2 had trouble remembering locations based on visual cues, “suggesting aspects of accelerated aging in brain-based hippocampal memory function,” Horvath said.

In other words, “You perform better if you have UCP2 versus if you don’t.”

These are mouse studies, he stressed, but the biological process of birth is similar in all mammals.

With C-section rates climbing, “I think the most we can do is to suggest to ask the question whether surgical delivery may also have impacts on brain neuronal circuit development in humans,” Horvath said.

Other studies show risks to babies from C-sections include neonatal respiratory distress. Risks to women include higher risks of hemorrhage requiring a hysterectomy, blood infections, wound infections and blood clots in the lungs.

As well, every C-section increases the risk that a woman will undergo a repeat one.

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