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December 15, 2006


[Rachel's introduction: "We have grave concerns about the trend for
caesareans," says Sakala. "Instead of going full-steam ahead,
shouldn't we be calling on the precautionary principle?"]

By Roxanne Khamsi

The massive surge in the maternal hormone oxytocin that occurs during
delivery might help protect newborns against brain damage, a new study
in rats suggests.

Researchers say the findings should encourage scientists to
investigate whether elective caesarean sections, which lack this
oxytocin surge, disrupt normal brain development.

Yehezkel Ben-Ari, a neuroscientist at the Mediterranean Institute of
Neurobiology in Marseille, France, and colleagues compared brain
tissue samples from rat pups born naturally or by caesarean section.
Brain cells from the naturally born pups did not fire in response to
the nerve signalling chemical GABA, the researchers found.

By comparison, at least 50% of the sampled cells from rats delivered
by caesareans responded to the GABA signals.

When the team gave pregnant rats atosiban -- a drug that specifically
blocks oxytocin's effects -- the brain cells from these rats were
easily excited by GABA. This revealed that oxytocin was the hormone
that made neurons from naturally delivered pups less receptive to

Natural safety net

Oxytocin levels surge dramatically during labour -- partly due to the
pressure exerted by the baby's head on the cervix -- along with other
hormones such as prostaglandins.

Ben-Ari believes that by "quieting" cells, oxytocin may prevent brain
damage due to oxygen deprivation that can occur during labour. In
fact, they found that the brain cells of rat pups delivered naturally
lived for an hour when placed in a solution that lacked oxygen. Brain
cells from pups with a mother whose oxytocin was blocked by atosiban
lived only 40 minutes.

By making cells less responsive, oxytocin reduces the oxygen they
require for energy production, the team says. The hormone could
provide a natural, temporary safety net to avoid damage from lengthy
or difficult deliveries, says Ben-Ari.

"It's like putting a television in standby mode to reduce energy
consumption," explains team member Rustem Khazipov.

Missing out?

Intense exposure to oxytocin during natural delivery might also
encourage brain cell maturation, says Ben-Ari. He wonders if babies
born by elective caesarean section miss out. "I think the oxytocin and
other hormones the mother is providing are important -- we should not
ignore them," he says.

In many places the rate of caesarean deliveries is going up. According
to the US National Institutes of Health, the rate has increased 40%
over the last decade and now accounts for three deliveries in every
10. This is partly due to a rise in the number of women having
elective caesareans, rather than for emergency delivery purposes.

"This is exactly the kind of study that gives me pause," says Carol
Sakala, director of programs at the New York-based Childbirth
Connection, a maternity care advocacy group. "We have grave concerns
about the trend for caesareans," says Sakala. "Instead of going full-
steam ahead, shouldn't we be calling on the precautionary principle?"

But others say it is too soon to view these findings as reason to
avoid c-sections wherever possible. "It is premature to translate
these findings into clinical practice for women," says Cynthia
Chazotte at the Albert Einstein College of Medicine in New York.

"While the fetuses delivered by elective caesarean will not have the
protective effect of oxytocin, they presumably will not be at the same
risk for [oxygen deprivation] as fetuses exposed to the stresses of
labour," says Ashley Roman at the New York University School of
Medicine. "I don't think that these results can be used to counsel
patients against elective caesarean delivery," she adds.