During
birth, hormones in the body surge in both mother and baby, sent along
by the nervous system. These stress hormones are there to spur delivery
and to help a baby adapt to living outside the womb. Some of the
transitions babies accomplish at birth include starting to breathe,
setting the body’s internal temperature and responding to microbes
passed along by the mother that help us regulate our immune system,
digestion and more.
Looking across the research literature,
however, Kenkel found that how one is born can have an effect on the
amount of stress hormones released at the time of delivery. For example,
vaginal delivery had the highest presence of birth signaling hormones,
followed by emergency cesarean, then scheduled cesarean with the lowest
levels.
He pointed out, too, that when babies are delivered by
cesarean section, some of these normal hormonal signals are disrupted,
or, in the case of scheduled C-section, never even started. How long
these hormonal differences last remains unknown. This led Kenkel to
question whether research should be looking at this more closely because
these hormones acting in early life are capable of developmental
programming, meaning they can cause permanent changes.
“Most
likely there is a very broad, but shallow effect occurring,” said
Kenkel, who is among only a handful of researchers considering the
hormonal implications of birth and the brain.
Other research,
particularly related to a healthy microbiome, has focused on whether
procedures should be used to reintroduce microbes that babies delivered
by cesarean may have missed out on.
Kenkel wonders if the same
idea could be used to introduce hormones in children that might not be
activated by cesarean delivery. This is not necessarily a new idea. For
example, premature infants are often given a hormone called cortisol to
help the lungs mature.
“We may want to investigate whether doing
a similar intervention makes sense in cesarean for any number of other
hormones to get the body off on the right foot,” he said.
While a
lot of research has looked at the hormone oxytocin and whether or not
it could play a role in the causes of autism, according to Kenkel,
cesarean delivery and obstetric interventions more broadly, are all
things that affect oxytocin signaling during this sensitive period
around birth.
“There are times in our development where hormones
have long-lasting consequences,” said Kenkel. “For example, if I were
to experience stress right now, I would generally recover quickly. In
early life, however, we are sensitive because we are still trying to
learn what the environment is going to be like. So, if my mom
experienced high stress levels while I was in utero, that tells me that
this environment that I’m going to be born into is a rough one, so I may
want to change my development to anticipate that.”
These
hormones are versatile, too. Oxytocin is well known for its role in
social bonding and helping mom bond with her baby, but evolution has
found a lot of other uses for it. Oxytocin is also really good at
regulating appetite, temperature and stress response.
“These
seemingly disconnected aspects of life share connections using the same
hormone; and when seemingly unrelated medical interventions affect those
hormones, it can translate into surprising outcomes,” he said.
If
he can establish that hormones during birth play a long-lasting role in
life, Kenkel said, it would lend evidence for research to explore
possible interventions that could be applied at birth to ensure
development that more closely resembles outcomes associated with a
vaginal delivery.
Kenkel published his findings in a paper in the Journal of Neuroendocrinology.
He
hopes the paper will open the door to new research ideas or directions
in this area, particularly greater collaborative research between the
fields of neuroscience and obstetrics, given the shared interest in
hormone mechanisms and early life.
“At this stage of our understanding, we just need a lot more information,” Kenkel said.
Article by Karen B. Roberts; graphic illustration by Jeffrey C. Chase.
Published Nov. 4, 2020.