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A new study focusing on pregnant women who have had a cesarean section says there is a need to better evaluate risks during a subsequent pregnancy and to bring down the overall C-section rates in Canada.

The study, released Monday in the Canadian Medical Association Journal, showed higher rates of complications, including mortality, for women who attempt a vaginal birth after a previous cesarean section, or VBAC, compared with women who instead scheduled a C-section beforehand. But those risks were still low − about 11 in 1,000 deliveries for VBAC compared with six in 1,000 for a repeated C-section.

The study also found those increased risks were largely due to failed VBAC deliveries that resulted in emergency C-sections. About half of VBAC deliveries failed and required an emergency C-section.

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A new study calls for closer evaluation of pregnant women who have had previous C-sections.Pascal Genest/Getty Images/iStockphoto

One of the authors, Carmen Young of the University of Alberta, said women who successfully undergo VBACs tend to have lower rates of adverse maternal and neonatal outcomes.

“Because the choice between delivery modes is so personal, it’s up to clients to evaluate and interpret the risks,” said Dr. Young, an assistant clinical professor in the University of Alberta’s department of obstetrics and gynecology.

“Our research highlights the importance of appropriate patient selection as well as the importance of careful monitoring in labour and delivery to optimize their safety.”

While her team’s study focused on VBAC deliveries, she emphasized the need to reduce the overall rate of C-section deliveries, which in turn would reduce the number of women who must choose on a subsequent pregnancy.

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The researchers used a database of all hospital deliveries in Canada between 2003 and 2015 and looked at pregnancies involving women who have had a previous C-section. While the study found a significant increase in risks, the absolute risks for both procedures were still low. For example, uterine ruptures were six times more likely for VBAC than a repeated C-section, but the risk to women in both of those groups was still below 3 per cent.

Dr. Young said both options should be offered to women. Due to the difficulty in accurately predicting whether a woman is a good candidate for VBAC, she suggests doctors and care providers consider the factors that resulted in the earlier C-section in the first place.

“If she tried for labour the first time and the baby didn’t fit through her pelvis, there’s a reasonable chance that’s going to happen again,” Dr. Young said. “But if the first cesarean section was scheduled because the baby was breached but this time the head is down, there’s a higher likelihood of her having a successful VBAC.”

Women planning to have a large family may also be motivated to try for a vaginal birth, as repeat C-sections increase surgical rates and a higher risk of placental problems.

“C-section rates are continuing to rise, and the most common single indicator for a cesarean delivery is a prior one,” Dr. Young said.

The Canadian Institute for Health Information recently released annual data showing that between 2016-17, almost 30 per cent of births in hospitals were through C-sections, though the rates varied significantly across the provinces and territories.

The optimal C-section rate in developed countries is between 10 per cent and 15 per cent, according to the World Health Organization. A more recent study in the Journal of the American Medical Association suggests it’s closer to 19 per cent.

B.C. Women’s Hospital and Health Centre is one of the largest maternity hospitals in Canada and, according to Communications Officer Holly Tran, cares for the province’s most high-risk pregnancies. In 2016-17, almost 33 per cent of births at the hospital were by cesarean section and more than one-third of those were elective.

According to Sarah Munro, postdoctoral fellow at Dartmouth College and the University of British Columbia, B.C. has been the province with the highest C-section rates since 2005, when it first passed the 30-per-cent mark.

“If it was a single issue with a single solution, we wouldn’t be seeing this trend continue,” Dr. Munro said.

Both Dr. Munro and Dr. Young agree that hospitals should bring in better training programs to equip staff with the skills required for breech vaginal deliveries, such as forceps and vacuum-assisted birth methods.

“It’s important to continue highlighting the higher-than-average C-section rates, and to support the care providers facing systemic challenges in their daily work,” said Dr. Munro, adding that the increasing rate is also costing hospitals double the amount that vaginal births do.

“But it’s also important that we don’t blame and shame families who have a C-section by choice or circumstance.”

Dr. Young also hopes her research will support autonomy in patient decision-making around childbirth.

“What we want people to take away from this is that when patients are properly selected and managed safely in labour and delivery, both options are reasonable and low risk.”

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