Trial of Vaginal Birth After a Caesarean Section (VBAC)

Approximately 1 in 4 pregnant women in Australia will be delivered via a caesarean section.  The most common indication amongst first time mothers is an emergency caesarean section for either fetal distress or failure to progress during labour. 

This usually raises the question “What is the best way for me to deliver my next baby?” 

A woman with a previous caesarean section has the choice of either having an Elective Repeat Caesarean Section (ERCS) or to attempt a Vaginal Birth After a Caesarean Section (VBAC).  This is a very personal choice and one that requires an open discussion with your obstetrician prior to the delivery of your baby.   There are usually a number of factors that will need to be taken into consideration to determine whether it is safe to proceed and its likelihood of success.
NB – For those reading American articles, a trial of VBAC can also be known as a TOLAC (Trial of Labour After Caesarean).
A VBAC offers a safe alternative to an elective caesarean section provided certain criteria are met.  These include:
  • Adequate patient selection,
  • Ongoing maternal care and support,
  • Continuous intra-partum fetal monitoring, and
  • A capable facility with readily available experienced personnel.
At Sunnybank Centre for Women we support a woman’s choice to attempt a VBAC provided this is safe mode of delivery for both the mother and her unborn baby.

Benefits of attempting a VBAC

There are many reasons why a newly expectant mother may choose to attempt a VBAC:
  • Shorter length of hospital stay and better post-partum recovery.  This is an important consideration especially for busy mothers with toddler(s).
  • Avoidance of surgical risk associated with another caesarean section such as wound infection, greater need for analgesia, and injury to other organs eg bladder.
  • A successful VBAC facilitates further vaginal births in subsequent pregnancies.  This is an important consideration for couples that are planning for a large family.
  • Reduced risk of breathing problems in the newborn.
  • Some women perceive a vaginal birth as a more fulfilling experience

Risks of attempting a VBAC

The two main risks that need to be considered when attempting a VBAC are a failed VBAC and uterine rupture.  Both of these complications require an emergency caesarean section.
  • Failed VBAC – Approximately 20-40% of women who attempt a VBAC will require an emergency caesarean section.  The most common reason is failure to progress.  Factors that decrease the likelihood of successful VBAC include:
    • No prior vaginal birth
    • Prior emergency caesarean section for obstructed labour (sp after failed instrumental delivery)
    • Advanced maternal age (>35yo)
    • Maternal obesity (BMI >30)
    • Large baby (>4000g)
    • Overdue pregnancy (>40 weeks gestation)
    • Need for labour induction (sp if unfavourable cervix / low Bishop score)
  • Uterine Rupture – For a woman with a single transverse lower uterine segment caesarean section (this is the most common type of uterine incision), the risk of a uterine rupture is approximately 1 in 200. 
    • The most serious maternal risk of a uterine rupture is the need for a hysterectomy (approx. 1 in 1000), while the most serious fetal risk is a hypoxic brain injury or a stillbirth (also approx. 1 in 1000). 
    • There are several factors that increase the likelihood of a uterine rupture and therefore make a patient unsuitable for a VBAC:
      • Short inter-pregnancy interval (<18 months)
      • More than one prior caesarean section
      • A vertical (“Classical”) or T-shaped uterine incision
      • Prior uterine rupture
      • Use of oxytocin for labour induction and/or augmentation

VBAC Success Rates

In general, 60-80% women who attempt a VBAC will have a successful VBAC.  Factors that increase the chances of an individual’s success include:
  • A previous vaginal delivery (sp a previous VBAC)
  • A prior caesarean delivery for anything else other than an obstructed labour
  • Spontaneous onset of labour
  • Favourable cervix at time of admission (>4cm dilatation)
  • Normal progress during labour
For further information and counselling for attempting VBAC, or if considering an elective repeat caesarean section, please contact Sunnybank Centre for Women on (07) 3345 4947 to make an appointment with one of our Obstetricians.  
Suite 5 171 McCollough Street
Sunnybank QLD 4109