Vaginal birth after Caesarian Section (VBAC), can quite safely be undertaken in the appropriate setting, with the appropriate patient and with experienced competent staff.
Overall, about 75% of women attempting VBAC will successfully have a vaginal birth. The great advantage of a successful VBAC is avoidance of the risks of surgery that come with a Caesarian Section, and also a far quicker recovery time.
The predominant risk of VBAC is the small risk of rupture of the previous Caesarian section scar during the labour. This is uncommon, reported to be about 1 in 200 VBAC attempts, but realistically the risk is probably lower than this when appropriate precautions are taken.
Previous Caesarean section scar rupture is a serious complication if it occurs, and there is a 10% chance of death to the baby if the scar ruptures, and there is a 10% chance the mother will need a hysterectomy due to heavy uncontrollable bleeding after delivery.
Reducing the risk of scar rupture is achieved by careful patient selection and pro-active management of the labour.
Women who are unsuitable for an attempt at VBAC include:
- Women who have had 2 or more Caesarian sections.
- Women who have had a prior “Classical” or T shaped incision on their uterus in a prior Caesarian Section.
- Prior fibroid removal when the cavity of the uterus has been entered during the surgery.
- Previous rupture of the uterus.
- Women who require induction of labour but have a cervix which is unfavourable for induction.
- The baby is presenting breech, or lying in a transverse position (i.e.- side on).
The management of the labour for a VBAC includes the following elements to reduce the risk of scar rupture and also to be prepared for any problems that may occur:
- An IV is placed in the hand for access into a vein and blood is sent for Group and Hold in case of any bleeding.
- The baby’s heart beat is monitored constantly via CTG tracing for the whole labour.
- Once the labour has commenced, the membranes are broken to release the fluid around the baby as this keeps the intensity in the contractions to keep the labour moving.
- Vaginal examinations are performed every 3-4 hours and the cervix must dilate at a rate of 1cm an hour to be considered adequate progress.
- After 50-60 minutes of pushing, an examination is undertaken and assistance with the delivery will be undertaken, using either a suction cup device or forceps to help the baby out. The pushing phase of the labour is when the prior Caesarean Section scar is under maximum stress, and rupture rates at their highest, hence the reason to have a safe limit on this time.
The two most common reasons for a VBAC to “fail” and an emergency Caesarean Section needs to be performed are:
- Concerns about the baby’s heartbeat on the CTG tracing which can mean the scar is weakening on in the early stages of rupturing
- The cervix fails to dilate appropriately, and the labour doesn’t progress. This will usually be due to the baby’s size being too large to fit through the mother’s pelvis.