What is a ‘vaginal birth after caesarean’ or VBAC?

A vaginal birth after caesarean (known as a VBAC) is when a woman who has had a caesarean has a vaginal birth down the track.

In Australia, about 12% of women have a vaginal birth for a subsequent baby after a caesarean. A VBAC is much more common in some other countries, including in several Scandinavian ones, where 45-55% of women have one.

So what’s involved? What are the risks? And who’s most likely to give birth vaginally the next time round?

What happens? What are the risks?

When a woman chooses a VBAC she is cared for much like she would during a planned vaginal birth.

However, an induction of labour is avoided as much as possible, due to the slightly increased risk of the caesarean scar opening up (known as uterine rupture). This is because the medication used in inductions can stimulate strong contractions that put a greater strain on the scar.

In fact, one of the main reasons women may be recommended to have a repeat caesarean over a vaginal birth is due to an increased chance of her caesarean scar rupturing.

This is when layers of the uterus (womb) separate and an emergency caesarean is needed to deliver the baby and repair the uterus.

Uterine rupture is rare. It occurs in about 0.2-0.7% of women with a history of a previous caesarean. A uterine rupture can also happen without a previous caesarean, but this is even rarer.

However, uterine rupture is a medical emergency. A large European study found 13% of babies died after a uterine rupture and 10% of women needed to have their uterus removed.

The risk of uterine rupture increases if women have what’s known as complicated or classical caesarean scars, and for women who have had more than two previous caesareans.

Most care providers recommend you avoid getting pregnant again for around 12 months after a caesarean, to allow full healing of the scar and to reduce the risk of the scar rupturing.

National guidelines recommend women attempt a VBAC in hospital in case emergency care is needed after uterine rupture.

During a VBAC, recommendations are for closer monitoring of the baby’s heart rate and vigilance for abnormal pain that could indicate a rupture is happening.

If labour is not progressing, a caesarean would then usually be advised.

Why avoid multiple caesareans?

There are also risks with repeat caesareans. These include slower recovery, increased risks of the placenta growing abnormally in subsequent pregnancies (placenta accreta), or low in front of the cervix (placenta praevia), and being readmitted to hospital for infection.

Women reported birth trauma and post-traumatic stress more commonly after a caesarean than a vaginal birth, especially if the caesarean was not planned.

Women who had a traumatic caesarean or disrespectful care in their previous birth may choose a VBAC to prevent re-traumatisation and to try to regain control over their birth.

We looked at what happened to women

The most common reason for a caesarean section in Australia is a repeat caesarean. Our new research looked at what this means for VBAC.

We analysed data about 172,000 low-risk women who gave birth for the first time in New South Wales between 2001 and 2016.

We found women who had an initial spontaneous vaginal birth had a 91.3% chance of having subsequent vaginal births. However, if they had a caesarean, their probability of having a VBAC was 4.6% after an elective caesarean and 9% after an emergency one.

We also confirmed what national data and previous studies have shown – there are lower VBAC rates (meaning higher rates of repeat caesareans) in private hospitals compared to public hospitals.

We found the probability of subsequent elective caesarean births was higher in private hospitals (84.9%) compared to public hospitals (76.9%).

Our study did not specifically address why this might be the case. However, we know that in private hospitals women access private obstetric care and experience higher caesarean rates overall.

What increases the chance of success?

When women plan a VBAC there is a 60-80% chance of having a vaginal birth in the next birth.

The success rates are higher for women who are younger, have a lower body mass index, have had a previous vaginal birth, give birth in a home-like environment or with midwife-led care.

For instance, an Australian study found women who accessed continuity of care with a midwife were more likely to have a successful VBAC compared to having no continuity of care and seeing different care providers each time.

An Australian national survey we conducted found having continuity of care with a midwife when planning a VBAC can increase women’s sense of control and confidence, increase their chance to be upright and active in labour and result in a better relationship with their health-care provider.