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Background

Planned VBAC - Best suited Further consideration/discussion Planned Elective Caesarean section (vaginal birth contraindicated)

Single previous caesarean section

In a singleton pregnancy

with cephalic presentation

at 37 weeks' or beyond,

with or without previous vaginal delivery.

Complicated uterine scars

Previous uterine rupture 

2 or more prior LSCS

Previous classical caesarean section

Other absolute indications to vaginal birth (e.g. major placenta praevia)

Comparison between Planned VBAC and Planned Elective Repeat Caesarean Section (from 39+0 weeks)

Criteria Planned VBAC Planned Elective Caesarean section
Uterine scar rupture
0.5% risk (1 in 200)
< 0.02% risk
Maternal death rate
4/100 000
13/100 000
Blood transfusion
2% (2 per 100)
1% (1 per 100)
Endometritis
No significant difference in risk
Transient respiratory morbidity
2 - 3%
4 - 5% (6% if delivery at 38 weeks instead of 39 weeks).
Hypoxic ischaemic encephalopathy
8 per 10 000
< 1 per 10 000
Perinatal death rate
4 per 10 000
< 1 per 10 000
Antepartum stillbirth (while awaiting spontaneous labour beyond 39+0 weeks)
10 per 10 000 (1.5 to 2 fold higher than women without previous LSCS)
--

Anal sphincter injury

5% (birth weight is the strongest predictor of this).

Rate of instrumental deliveries - increased upto 39%.

--
Other benefits
72 - 75 % chance of successful VBAC, if successful, shorter hospital stay and recovery.

Less risk of - pelvic organ prolapse and urinary incontinence.

Option for sterilisation.

Future pregnancies
Increased chances of future vaginal birth
Increased risk of placenta praevia/accreta and adhesions.

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VBAC Success Rate

Success rate of planned VBAC is 72 – 75%.

Previous vaginal delivery, particularly previous VBAC, is the single best predictor of successful VBAC.  It is associated with a planned VBAC success rate of 85 – 90%.

Previous vaginal delivery is also independently associated with a reduced risk of uterine rupture.

Greatest risk of adverse outcome occurs in a trial of VBAC resulting in emergency caesarean delivery.

In induced and/or augmented labour (compared with spontaneous VBAC labour), there is 2 – 3 fold increased risk of uterine rupture and 1.5 fold increased risk of caesarean delivery

Induction of labour using mechanical methods (amniotomy or Foley catheter) is associated with a lower risk of scar rupture, compared with induction using prostaglandins.

Higher VBAC success rate with :-

  • Greater maternal height
  • Maternal age less than 40 years
  • BMI less than 30
  • Gestation of less than 40 weeks
  • Infant birth weight less than 4 kg
  • Spontaneous onset of labour
  • Vertex presentation
  • Fetal head engagement or a lower station
  • Higher admission Bishop score
  • Previous caesarean for fetal malpresentation
  • Younger women
  • White ethnicity
  • Elective caesarean section in previous delivery (emergency caesarean in first birth, particularly failed induction of labour is associated with lower VBAC success rate).

Intrapartum Care - VBAC

Planned VBAC should be conducted with continuous intrapartum care and monitoring.

Continuous electronic fetal monitoring for the duration of planned VBAC, commencing at the onset of regular uterine contractions.

Women with unplanned labour and a history of previous caesarean delivery should have a discussion with an experienced obstetrician to determine feasibility of VBAC.

Epidural analgesiaNOT contraindicated in a planned VBAC. 

Increasing requirement for pain relief should raise awareness of the possibility of an impending uterine rupture

Elective Repeat Caesarean Section (ERCS)

ERCS should be conducted after 39+0 weeks of gestation.

Antibiotics should be administered before making the skin incision in women undergoing ERCS.

All women undergoing ERCS should receive thromboprophylaxis.

Early recognition of placenta praevia.

Risk of placenta praevia in subsequent pregnancies with one, two or three or more previous caesarean deliveries experience a 1%, 1.7% or 2.8% risk respectively.

Risk of uterine rupture before labour with a previous classical incision on the uterus is 2%.

Special Circumstances

Uncertainty about safety and efficacy of planned VBAC in pregnancies complicated by :-

  • post – dates
  • twin gestation
  • fetal macrosomia
  • antepartum stillbirth
  • maternal age of 40 years or more.
  • short inter-delivery interval.
  • lower pre – labour Bishop score.

Planned preterm VBAC has similar success rates to planned term VBAC but with a lower risk of uterine rupture.

VBAC Score

VBAC Score has been studied to predict the success of women attempting VBAC.

It consists of five features :-

  • Admission Bishop score
  • Age
  • Previous caesarean delivery indication
  • BMI
  • Previous vaginal birth

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Revise Numbers and Percentages in this article.

Success rate of planned VBAC is 72 – 75%.

Previous vaginal delivery, particularly previous VBAC, is the single best predictor of successful VBAC.  It is associated with a planned VBAC success rate of 85 – 90%.

Rate of uterine scar rupture0.5% with planned VBAC and < 0.02% with elective caesarean section. 

Risk of uterine rupture before labour with a previous classical incision on the uterus is 2%.

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