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Caesarean Section Timing Can Put Babies at Risk

Caesarean section is a surgical procedure that sometimes becomes necessary when a woman in labor experiences a physical problem, or if the baby is in distress passing through the birth canal. After one Caesarean, or C-section, women face a slightly increased risk (about 1 in 100 cases) for ruptured uterus in delivering future babies vaginally. So, when available, women frequently choose to deliver subsequent babies via C-section.

Now new research from the University of North Carolina finds that the timing of these repeat C-sections can be critical for the health of newborns. Dr. John Thorp helped gather and analyze data from several dozen hospitals around the U.S. They collected data on tens of thousands of births and focused on women who had repeat C-sections.

"The rate of Caesarean sections is about 30 percent, about one out of three [deliveries]," Thorp says. "About one out of three of those, or 10 percent over all, are repeat Caesarean sections for which the timing is elective, meaning that the surgeon and the patient choose the times."

Thorp says the timing is critical. He and his colleagues found babies do best when they're delivered by C-section close to a woman's due date - between the 39th and 40th weeks of pregnancy.

"If the delivery occurred a week prior to that critical window… babies were two times more likely to have feeding or breathing problems," Thorp reports. "If [C-sections] were done two weeks before that critical window of 39 to 40 weeks, then they were at fourfold that risk."

Thorp and his colleagues also found that babies who stayed in utero for longer than 40 weeks had breathing and feeding problems, too. A significant number of those infants also developed infections. He says the problem is more acute when women and their doctors plan the birth for their own convenience and ignore the baby's schedule. Thorp posits that babies somehow signal the beginning of the labor process - probably through a hormonal process.

"And… when we choose to do an elective repeat Caesarean section, we circumvent that signal," Thorp says. "And when we circumvent that signal, then the likelihood of problems go up."

Thorp says his research doesn't answer the question of whether or not it's a good idea to do elective Caesarean sections. But for women who do choose the procedure, he says these findings show the importance of timing the procedure to reduce problems for the baby.

Thorp's research is published in the New England Journal of Medicine.