Written by Dr Ryan Lee, Consultant obstetrician and Gynaecologist Specialist
VBAC stands for “Vaginal Birth After Caesarean Section”. This means giving birth vaginally (either normal delivery or assisted by using forceps or vacuum cup) after having had a previous caesarean section.
VBAC should be recommended in women who had a single previous lower segment caesarean section delivery (LSCS), with or without a history of previous vaginal birth if there are no contraindications for vaginal delivery.
Planned VBAC is relatively safe and may be offered to the majority of women with a singleton pregnancy with cephalic presentation who have had a single previous lower segment caesarean delivery, with or without a history of previous vaginal birth.
VBAC has a higher success rate when the woman labours spontaneously and the previous caesarean section was for a non-recurrent indication.
Decision for VBAC should be individualised. In formulating a clinical management plan, respect for the woman’s autonomy and participation of her and her partner in the decision making is of paramount importance.
Antenatal counselling for VBAC should include a discussion on:
(1) Success rate
- unselected population 72-75%
- previous successful VBAC 85-90%
(2) Uterine rupture risk
- Uterine rupture risk
- 0.5 % without induction/augmentation of labour
- 0.8 % with oxytocin
- 2.5% with prostaglandin
- Risk is halved in patients with previous successful VBAC
(3) Cosideration to future family planning
- greater number of caesarean sections, greater morbidity (placenta accreta/increta/percreta and associated risk of haemorrhage/adhesions)
(4) 4-7/10000 (0.04 to 0.07%) risk of perinatal death (comparable to risk for nulliparous women in labour)
- 8/10000 (0.08%) risk of HIE
(5) 1% additional risk of requiring blood transfusion
Suitability for VBAC
Your doctor will evaluate your previous pregnancies and medical history. If you have had one previous uncomplicated caesarean section and your current pregnancy has been straightforward, you may choose to attempt a VBAC. Some factors to determine suitability for VBAC are as follows:
Previous caesarean section
Type of incision.
- Classical C-section” refers to a vertical incision in the upper part of the womb. Women who had a previous classical caesarean section are not advisable to attempt vaginal birth as there is a high risk of scar separation/tear (rupture).’
- Lower segment C- section” refers to a horizontal incision on the lower part of the womb. This method is associated with a lower risk of scar rupture and women with this type of incision may opt for VBAC after one previous caesarean section.
Reason for the previous caesarean section. If the reason for previous caesarean section due to cephalopelvic disproportion (CPD), where the pelvis is too small to allow the passage of the baby’s head, VBAC may not be suitable.
Complications during the previous caesarean section. If the previous caesarean section was complicated by unexpected tears in the uterus, your obstetrician may advise for repeat caesarean section in the subsequent pregnancy.
Current pregnancy
Certain conditions such as a low-lying placenta or abnormal presentation such as breech presentation is unsuitable for VBAC.
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 surgery to remove fibroids may increase the risk of rupture of the womb during labour. Hence VBAC may not be suitable.
Likelihood of a successful VBAC
About 60 to 70% of woman with a straightforward pregnancy will achieve a successful VBAC after one caesarean section. Women who have had previous vaginal birth before or after your caesarean section, especially if you have had a previous successful VBAC have a higher success rate of 80 to 90%.
Advantages of a successful VBAC as compared with elective caesarean delivery
A successful VBAC has fewer complications as compared with elective caesarean delivery. You will have a greater chance of a vaginal birth in future pregnancies, quicker recovery with shorter hospital stay, lesser bleeding and post-delivery pain, lesser chance of needing blood transfusion and getting an infection. You can also avoid risks of caesarean delivery and your baby will have lower risk of getting initial breathing problems.
Emergency C-section
If you need an emergency caesarean section during labour, there are higher risks of complications for the mother as compared to an elective caesarean section. The costs of a failed VBAC would also be higher.
Complications associated with VBAC
The primary concern associated with VBAC is the risk of scar separation/tear (rupture). The incidence of scar rupture is less than 1% after one previous lower segment caesarean section. If there are warning signs of scar rupture, your baby will be delivered by emergency caesarean section.
Serious consequences due to scar rupture are rare and include massive blood loss, a need for surgical removal of the womb (hysterectomy) and ICU stay in the mother, and also fetal death or cerebral palsy (neurological impairment) for the child. These consequences can sometimes be life-threatening for both you and your baby.
Planning for a VBAC
You will be advised to come to the labour ward early once you start having regular contractions or when your waters break, so that your baby’s heartbeat can be monitored continuously during labour as any change in the heartbeat pattern can be a sign of scar rupture. An emergency caesarean section will be performed in this case.
