The risk of vaginal birth after C-section

According to the latest statistics, 28.2 per cent of births in Canada were caesarean births. C-sections are on the rise in this country, up one point five per cent over the past year alone.

Some women who have had a C-section in the past may want the option of a vaginal birth. The decision is more controversial than it sounds.

The controversy surrounds the risk and benefit of attempting what doctors and midwives call a VBAC, which stands for vaginal birth after a single previous C-section. If a woman has had more than one, VBAC is considered too risky.

Potential risks associated with VBAC include tearing or rupturing of the uterus or womb during childbirth. That is a catastrophe that can result in the baby’s death. There is also an increased risk of hemorrhage during and following the birth, plus other risks to mother and baby. Those risks have made some obstetricians reluctant to attempt a VBAC.

Assessing the risk

study by researchers from Canada and Saudi Arabia just published in the Canadian Medical Association Journal was designed to assess the risk.

It looked at women across Canada (excluding Quebec) who had a previous caesarean birth followed by a subsequent pregnancy between 2003 and 2015.

Compared to women who had a repeat C-section, those who attempted a VBAC had a significantly higher relative risk of ruptured uterus (6.4 times more likely) and a greater relative risk of severe hemorrhage following the birth.

They were nearly twice as likely (1.96) to have severe complications including dying in childbirth.

Keep in mind that those are relative risks. Whether they had a VBAC or a repeat C-section, the absolute risk of harm to the mother was low.

The overall rate of severe complications to the baby was significantly higher among women who had VBAC compared to women who had a repeat C-section.

There was a higher rate of seizures. The death rate among VBAC newborns was also higher but not enough to reach statistical significance.

Like maternal deaths, newborn deaths are highly unusual in our health-care system, so the increased risk doesn’t translate into many more deaths.

C-section births on the rise

There was one unexpected finding. Newborns fared a bit worse in 2015 than they did at the beginning of the study back in 2003. Maternal outcomes did not get worse over time. Researchers aren’t sure why; it’s something that needs more study.

The study took place at a time when C-section births are on the rise. Doctors and the people who run the health-care system are uncertain as to why.

The most obvious reason is that more C-sections result in more repeat C-sections. Another reason may be the average age of pregnant women is on the rise.

C-sections may be recommended to reduce the risk of complications that rise with age. Rates of obesity in pregnant women are also going up. With obese mothers, the womb doesn’t contract as well, prompting the need for more C-sections.

Some doctors think convenience and personal choice play a role in rising rates.

The authors of the study say that a planned VBAC has been promoted by some as safe. They wonder if the increase in adverse effects seen in this study mean that women aren’t being selected carefully enough to make sure VBAC is suitable for them.

In 1999, the American College of Obstetricians and Gynecologists recommended that VBAC be attempted only if well-equipped emergency care is available on a moment’s notice.

In 2005, the Society of Obstetricians and Gynaecologists of Canada recommended that VBAC be done in hospital where timely access to C-sections is possible.

This study doesn’t sort out the controversy. Making sure you have access to a C-section if and when necessary seems like a sensible choice.
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