Elective C-Section: 38th Week Too Soon

Babies born by elective C-section before the 39th week of
pregnancy have a three- to
fourfold higher risk of breathing trouble than babies whose mothers have
a normal vaginal delivery.

Elective C-section babies also have a fivefold higher risk of needing
mechanical breathing assistance for serious respiratory trouble, find Anne
Kirkeby Hansen, MD, and colleagues at Denmark's Aarhus University Hospital.

"Mothers who choose elective cesarean section should be aware that the
risk of respiratory problems is four times raised at 37 weeks' gestation vs.
full-term, intended vaginal delivery," Kirkeby Hansen tells WebMD. "The
rate of respiratory problems is 10% for elective C-section at 37 weeks, but it
is 2.8% for intended vaginal deliveries. That is why we say you should never do
elective cesarean section at 37 weeks."

Kirkeby Hansen and colleagues gathered data on the 34,458 babies born in
Aarhus, Denmark, from 1998 through 2006. Nearly 2,700 of these infants were
delivered via elective C-section -- that is, the mother or her obstetrician
opted for C-section without having a medical need to so.

The researchers compared these infants to infants from women who tried to
have a vaginal delivery, including women who ended up having a C-section.

After adjusting for factors that might affect the infant's breathing,
Kirkeby Hansen and colleagues found that children delivered by elective
C-section at 37 weeks' gestation had a 3.7-fold higher risk -- and at 38 weeks,
a 3.0-f old higher risk -- of
transitory tachypnea of the newborn (a condition sometimes called wet lung),
respiratory distress syndrome, or persistent pulmonary hypertension (dangerously high blood pressure in the
lungs).

All of these conditions mean that a baby is placed in an incubator in the
neonatal intensive care unit for two days or so, Kirkeby Hansen says.

Most children fully recover from these breathing problems, notes Emory
University pediatrician Lucky Jain, MD. But the long-terms effects aren't
clear.

"Sometimes these babies get into bigger trouble in the neonatal
ICU," Jain tells WebMD. "And what we don't yet understand well is the
impact of two or three or four days of separation from the mother, of not
initiating breastfeeding , and of exposure
to bacteria that are not normally found in our bodies."

Although it happened much less often, the Danish researchers found that
children delivered via elective C-section at 37 weeks' gestation have a
fivefold higher risk of serious breathing problems requiring oxygen therapy, a
continuous positive air pressure device, or mechanical ventilation. For
elective C-sections at 38 weeks' gestation, this risk is 4.2 times higher than
for intended full-term vaginal delivery.

Labor Good for Fetus

What does a C-section have to do with a newborn's ability to breathe?

As it leaves the liquid environment of the womb, a newborn faces the
enormous challenge of making the transition to breathing air. Its fluid-filled
lungs must clear quickly, Jain notes.

"There are many reasons why a baby born after elective C-section is more
prone to delayed transition to air breathing," Jain says. "The first is
reduced gestational age. And in the last trimester of pregnancy, every week
counts. A 37-weeker is much more prone to respiratory issues than a
39-weeker."

Kirkeby Hansen and Jain note that during labor, a woman secretes powerful
stress hormones. This triggers stress-hormone secretion in her fetus. The
hormones have two effects on the fetal lungs. They speed the absorption of
liquid. And they increase secretion of surfactants, natural substances that
help clear liquid from the lungs.

"Once a woman is in labor, all this gets started," Kirkeby Hansen
says. "In women who do not have labor, this process is not believed to
start."

Jain says labor is the most reliable sign that a baby is ready to be
born.

"When mother nature alls on spontaneous labor to start, it mostly is
accurate in terms of the biologic clock and a good likelihood the baby is
mature," he says. "But when we do it by elective C-section, we trust
mothers' last-period dates or ultrasounds performed early in pregnancy, and
those calculations are not always accurate."

Nearly a third of U.S. pregnancies now end in C-sections, Jain says. Over
the last decade, as the C-section rate has climbed, the average gestational age
at birth for U.S. babies has dropped from 40 weeks to 39 weeks.

On the one hand, Jain notes, research shows that delivering infants at 39
weeks' gestation or less cuts the risk of stillbirths. On the other hand, early
delivery clearly has its own risks -- to the infant as well as to the
mother.

"The obstetric community has to get its arms around the fact that
C-section has never been proven to be safer for the mother," Jain says.
"A study that appeared last year showed that when you look at mothers with
no identified risk who have had a C-section -- with no medical indication
either from the mother or from the fetus -- there was higher mortality in the
mother and in the baby."

Kirkeby Hansen advises women seeking elective C-section to wait until the
39th week of their pregnancy.

"A woman should make sure she is not having her C-section too early. She
should put her foot down and not have it at 37 or 38 weeks just because this
fits into the hospital's plan," she says. "I personally would not have
one before 39 weeks."

"Thirty-nine weeks' gestation is a minimum. It may be ideal," Jain
says. "But 38 weeks is not term gestation in my mind, and women need to be
very careful with that. When a vaginal birth occurs at 38 weeks it is very
different from an elective C-section at 38 weeks. And the decision to undergo
C-section, especially at a mother's or an obstetrician's choice, with no
medical indications, needs to be carefully thought through, and parents need to
ask their obstetrician about the evidence for and against it."

Kirkeby Hansen and colleagues report their findings in the Dec. 12 online
edition of BMJ.

By Daniel DeNoon
Reviewed by Louise Chang
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