Most women who have a c-section want to know what is the chance of having a vaginal birth in the future.

Unfortunately there’s no crystal ball to predict with complete certainty which women will have a successful vaginal birth after c-section.

However there are certain factors which can help to indicate who might be successful.

What Is The Chance Of A Vaginal Birth After C-Section?

The following are the 4 main factors that can affect your chances of successfully achieving a vaginal birth after c-section (VBAC). It’s important to bear in mind these factors don’t mean you can’t have a VBAC, but it’s also important to be informed and take your risk factors into account.

#1: Weight

One of the factors which can affect your chance of a successful VBAC is how much weight you gain between your previous pregnancy and the next.

Research has shown specifically how women gaining or losing weight between pregnancies can affect the chances of a successful VBAC. The study showed:

Women in a normal weight range whose BMI increased 1-2 were 7% less likely to have a VBAC. An increase of 2+ BMI lowered their chance by 13%.
Overweight women whose BMI decreased by at least 1 had a 12% increased chance of a successful VBAC.
Obese women increased their chance of a VBAC by 24% if their BMI was lowered by at least 1.

Although BMI is the main way health professionals measure weight gain or loss during pregnancy, it is becoming clear the issue isn’t as simple as that.

If you want to achieve a successful VBAC for your next birth, it is vital you maintain your health – not just in terms of your weight, but also to reduce your risk of pregnancy complications. Seek out a supportive health professional who can work with you to achieve a healthy weight range for you.

#2: Maternal Age

Statistically speaking, women over the age of 35 are more likely than their younger counterparts to have a c-section. Research bears this out: women over 35 who try for a VBAC are less likely to succeed, as well as having an almost 40% increased risk of VBAC-related operative complications.

The most important reason why maternal age seems to be a factor in the success of a VBAC is related to health problems that are more likely to occur as women age.

You can read more about this in Over 35 And Having A Baby – What You Should Know.

There is little you can do about your age but being informed about having a low risk pregnancy will increase your chance of a successful VBAC.

#3: Baby Weight

According to some sources, having a baby weighing more than 4kgs reduces the chance of a successful VBAC.

When we look at the evidence around suspected big babies, it’s clear much of the increased risk relates either to shoulder dystocia or to uterine rupture.

Shoulder dystocia is when a baby’s shoulders become ‘stuck’ during birth. It occurs very rarely, in only about 1% of vaginal births. Although the risk of shoulder dystocia appears to be increased with larger babies, research shows it can occur in any situation.

Uterine rupture during a VBAC is a major concern for all care providers. There is a lack of clear information available to women with regard to uterine rupture; many are not aware the overall risk of this happening is 1%.

Many sources suggest there is an increased risk of uterine rupture if a baby weighs more than 4kgs and the mother has had a previous c-section. This retrospective study, however, concluded there was no significant association between VBAC of a big baby and uterine rupture.

If your baby is suspected to be over 4kgs and you’re trying for a VBAC, make sure you’re aware of all the facts before making a decision about your birth.

You can read more in What Is Considered To Be A Big Baby?.

#4: Reason For Previous C-Section

C-section rates are pretty high in countries such as Australia, the UK and the US. Often they’re performed after labour has begun; this is called an emergency or unplanned c-section.

The reason why you had a c-section previously can have an impact on how successful your VBAC is in your next birth.

If your previous c-section occurred because of something that isn’t likely to happen again then your chance of a successful VBAC will be increased.

These factors include those to do with the baby’s health, rather than factors connected with the actual labour.

They are:

Breech presentation of baby
Placenta previa
Fetal distress

If you have had a vaginal birth since your c-section, you are even more likely to succeed with a future VBAC.

Am I A Good Candidate For VBAC?

Women who have experienced the following aren’t considered to be good candidates for VBAC:

Prolonged/stalled second stage of labour and previous c-section
No fetal descent into the pelvis
The reason for previous c-section still exists
Your previous c-section was performed with a vertical incision
You’ve had more two or more c-sections with no successful vaginal births
You are pregnant with multiple babies.

Your care provider might still consider a trial of labour but could be governed by policies including continuous fetal monitoring and restricted pregnancy gestation or labour duration. Talk to your care provider about how these might affect your ability to have a successful VBAC.

How Can I Increase My Chance Of A Successful VBAC?

Most women who try for a VBAC will be successful. Having a healthy pregnancy and choosing a VBAC supportive care provider will help you to plan for a successful vaginal birth after c-section.

Your care provider is a key part of your VBAC success.

Be as informed as you can be about the ways to improve your chances, by reading VBAC Sabotage – 9 Things That De-Rail Your VBAC Attempt.