What Is VBAC?
VBAC is the acronym for "Vaginal Birth After Caesarean section".
If I Had One Previous Caesarean Section Birth, Can I Go Through A Subsequent Vaginal Birth?
Women who have had one previous uncomplicated lower segment caesarean section (LSCS) and no other adverse obstetric feature in the current pregnancy are suitable candidates for VBAC. Generally, the relevant factors to determine suitability for VBAC are as
- The type of previous caesarean section
- Type of incision: This refers to the manner in which the uterus was incised during the delivery in the last pregnancy.
- "Classical section" refers to a vertical incision on the upper part of the uterus. Women who a previous classical caesarean section should not opt for VBAC as there is a higher risk of uterine rupture or tear.
- "Lower segment caesarean section" refers to a horizontal incision on the lower part of the uterus. This method is associated with a lower risk of uterine rupture and women with this type of incision may opt for VBAC.
- Reason for previous caesarean section: If the reason for the previous caesarean section is a recurring one such as contracted pelvis (i.e. where the pelvis is too small to allow the passage of baby due to some form of obstruction), then VBAC is unsuitable.
- Complications during the previous caesarean section: If the previous caesarean section was complicated by unexpected tears in the uterus, the obstetrician may advise the need for repeat caesarean section in the subsequent pregnancy. VBAC should not be considered in such a case.
- Current pregnancy: Certain conditions such as low-lying placenta or abnormal presentation of the baby in the present pregnancy may prevent a safe vaginal delivery.
- Other medical / surgical problems: Certain medical conditions such as certain heart diseases or severe hypertension would prevent a woman from enduring the physical stress of a vaginal delivery. Previous operation on the uterus to remove fibroids may result in weakening of the muscle wall of the uterus and increase the likelihood of uterus rupture during labour. In such cases, the risk and benefits of VBAC may have to be considered carefully.
The chance of a successful VBAC is between 60% and 70%. It is generally higher for women who have had previous successful vaginal deliveries. The chance of success may be lower if the reason for the previous caesarean section was due to cephalopelvic disproportion (i.e. where the baby is relatively too big to pass through the maternal pelvis).
What Are The Advantages Of VBAC As Compared With Elective Caesarean Section Delivery?
A successful vaginal birth is beneficial to the mother as it is generally associated with less bleeding, less blood transfusion, less infection, faster recovery with shorter hospital stay and less post-delivery pain and complications.
Successful VBAC has also no proven adverse effect on the baby. In terms of cost, a successful VBAC is cheaper than caesarean section birth.
The primary concern associated with VBAC is the risk of uterine rupture or tear. The incidence of uterine rupture is quoted as:
- Less than 1% after one previous lower segment caesarean section
- 1 - 5 % after two previous lower segment caesarean sections
- 4 - 9% after a classical uterine scar
Although it occurs rarely, uterine rupture can be life-threatening for both the mother and child. It may also result in the need for surgical removal of the womb (hysterectomy) for the mother as well as neurological impairment of the child (cerebral palsy).
In addition, if the trial of labour fails and the mother needs an emergency caesarean section, there may be higher risk of complications for the mother as compared to an elective or planned caesarean section or a successful VBAC. The costs of a failed VBAC would also be higher.
What Are The Precautions My Obstetrician Will Exercise To Minimise Complication Associated With VBAC?
Before the decision for VBAC can be made, the obstetrician would:
- Review the medical records for the previous pregnancy to assess the reason for the last caesarean section and the operation procedure to determine if there were any complications during the operation and the possible need for repeat caesarean section.
- Assess the current pregnancy to see if the patient is suitable for vaginal delivery. Relevant factors include the location of placenta, baby's presentation and the adequacy of the maternal pelvis relative to the baby's size.
- Discuss with you the suitability for VBAC and the associated risks and benefits.
- If desired and found to be suitable for VBAC, you will be allowed a short trial of labour. During labour, your baby will be continuously monitored to ensure his wellbeing. The need for induction or augmentation of labour is left to the obstetrician's discretion based on his assessment of the situation. An emergency caesarean section would be performed if there are signs of foetal distress or if the labour is not progressing as well as expected.
Epidural is commonly used in labour to provide effective pain relief. It is safe and not associated with late detection of uterine rupture.
In addition, if trial of labour fails, epidural can be continued as a form of anaesthesia for emergency caesarean section to be carried out. Therefore, epidural can be chosen as a good form of pain relief while undergoing VBAC.
Apart from epidural, there are other options for pain relief such as breathing exercises, back massage, entonox gas, pethidine injection etc.
Can I Make My Own Decision For Or Against VBAC?
A decision for or against VBAC should be a joint decision between you and your obstetrician after having taken into consideration the pros and cons of VBAC in your situation.
This featured article is contributed by the Department of Obstetrics & Gynaecology, KK Women's and Children's Hospital. To read more please visit www.kkh.com.sg/HealthPedia.