Vaginal birth after caesarean section

Several years ago, the expression “once a C-section, always a C-section” was commonplace. However, experts have agreed since the 1908s that vaginal delivery is a safe option for most women who have had a caesarean section for a previous pregnancy. This is called a vaginal birth after caesarean section (VBAC). In Quebec, about 1 in 5 women who have had a C-section give birth vaginally during their next pregnancy.

A successful VBAC depends largely on the reasons for the first caesarean section and the progress of the current pregnancy. Most studies on women who attempt a VBAC put the chance of success at about 75%. If the labour is not successful, the medical team will perform another C-section. As with any other health decision, the decision to have a VBAC rests primarily with the pregnant woman.

The benefits of VBAC and of a repeat caesarean section

Several factors may lead a woman to choose a VBAC or caesarean section for their next delivery. Health care professionals should consider the goals and desires of the mother.

The benefits of a vaginal delivery after caesarean section

• It favours skin-to-skin contact immediately after birth.
• It may facilitate breastfeeding.

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• The hospital stay will likely be shorter.
• You may recover more quickly after giving birth.
• It avoids the pain associated with surgery.
• It provides the satisfaction of giving birth naturally.

The benefits of a repeat caesarean section

• You already know what to expect, as you’ve already experienced a C-section.
• You will know the date of the birth in advance.
• It’s easier to plan parental leave.
• You will not experience the pain of contractions during labour.

VBAC and repeat C-section risks

Both VBACs and repeat C-sections carry risks. Women who become pregnant after a C-section should talk to their health care provider about the risks associated with each type of delivery.

VBAC risks

• Uterine rupture. This is the main risk associated with a VBAC. A uterine rupture occurs when the lining of the uterus tears. This can happen during any delivery, but the risk is greater after a C-section because the incision made during the procedure may have weakened part of the uterus. A uterine rupture may require an emergency C-section, a blood transfusion, or even the removal of the uterus. The baby may partially exit the uterine cavity or may not get enough oxygen.
  However, the risk of uterine rupture is low, affecting just 5 to 9 out of every 1,000 women (0.5% to 0.9%) who attempt a VBAC. Women who have had more than one C-section have a slightly higher incidence of uterine rupture, ranging from 9 to 37 out of every 1,000 women (0.9% to 3.7%).
• Unplanned C-section. If labour is not successful, the team will need to perform a caesarean section. Approximately 25% of women who attempt a VBAC will require this surgical procedure.
• Complications associated with a normal delivery. A VBAC carries the same risk of complications as any vaginal delivery. These complications are no more common with a VBAC than with a first-time delivery. For example, during a VBAC, the woman giving birth may have an episiotomy or need a vacuum- or forceps-assisted delivery.

Repeat caesarean section risks

• Complications associated with C-section surgery. A caesarean section increases the risk of infection, blood clots, removal of uterus, and hemorrhaging.
• Issues with future pregnancies. In women who have given birth by caesarean section, the placenta is more likely to develop abnormally in subsequent pregnancies.
• Breathing problems in the baby.
• Certain chronic diseases in children. Children born by C-section are more likely to suffer from asthma or develop allergies.
• Difficulties associated with premature birth. Repeat caesarean sections are often scheduled for the 39th week of pregnancy. If the expected date of delivery was miscalculated, the baby could be born prematurely.

According to the Ministère de la Santé et des Services sociaux (MSSS), a repeat C-section could cause more complications for the woman than a vaginal delivery after a C-section.

Factors that increase the likelihood of a successful VBAC

The chances of a successful VBAC vary from woman to woman. Here are some factors that increase the likelihood that a woman will give birth vaginally after a C-section.

• A low transverse (horizontal) incision from their previous C-section. Experts estimate that 90% to 95% of women who have had a C-section have this type of incision.
• A first C-section that was performed for a reason that will not occur again (e.g., a breech baby).
• The mother has already given birth vaginally.
• Labour is allowed to start spontaneously.
• The mother has already had a successful VBAC.
• The cervix is effaced and dilated during childbirth.

The following factors decrease the likelihood of a successful VBAC

• The first C-section was performed because labour stalled.
• The fetus’s head is not engaged in the mother’s pelvis at the time of delivery.
• Labour is induced or stimulated by pharmacological means. Certain medications may increase the risk of uterine rupture. Prostaglandins in particular can cause biochemical changes that weaken the scar. The Society of Obstetricians and Gynaecologists of Canada advises against their use in women who have had a caesarean section.
• The mother is more than 40 years old.
• The mother is obese.
• The baby’s weight is estimated at more than 4 kg.
• The interval between the previous C-section and the expected delivery date is less than 18 to 24 months.
• The mother has chronic health problems, such as preeclampsia, hypertension, diabetes, or kidney disease.
• Delivery takes place after the 40th week of pregnancy.

In some situations, a vaginal delivery after a C-section is contraindicated. This is the case for women who have had a caesarean section with a vertical or T-shaped incision. The risk of uterine rupture is 10% to 12% in these cases. Women who have experienced a uterine rupture or had uterine surgery are also not candidates for a VBAC. In these cases, the medical team will schedule a C-section at 39 weeks of pregnancy, which is before labour begins.

Ensuring the best chance of success

While a successful VBAC is largely dependent on the circumstances of your previous C-section and the progress of your current pregnancy, there are some contributing factors that are within your control.

• Stay motivated.
• Find a doctor or midwife who supports VBAC.
• Ensure that you have support and guidance during childbirth.
• Change positions often during labour and favour those that facilitate cervical dilation.
• Eat and drink in small amounts during labour to keep your energy up.
• Urinate frequently to keep your bladder empty.
• Use relaxation techniques.
• Push in a standing or squatting position.

Things to keep in mind

• Vaginal delivery is a safe option for most women who have previously had a C-section.
• A successful VBAC depends largely on the reasons for the first caesarean section and the progress of the current pregnancy.
• Choosing between a VBAC and a repeat C-section is not easy. Talking to the health care professional who is monitoring your pregnancy will help you make an informed choice.

Scientific review: Hélène Vadeboncoeur, retired perinatal researcher and author of Une autre césarienne ou un AVAC? Research and copywriting: The Naître et grandir team Updated: December 2021

Photos: iStock.com/digitalskillet (top) and bukharova (bottom)