In addition to these evidence-based recommendations, the guideline development group also identifies points of best clinical practice in the original guideline document.
Levels of evidence (Ia-IV) and grading of recommendations (A-C) are defined at the end of the "Major Recommendations" field.
Antenatal Counselling
How Should Women be Counselled in the Antenatal Period?
B - Women considering their options for birth after a single previous caesarean should be informed that, overall, the chances of successful planned vaginal birth after previous caesarean section (VBAC) are 72 to 76%.
All women who have experienced a prior caesarean birth should be counselled about the maternal and perinatal risks and benefits of planned VBAC and elective repeat caesarean section (ERCS) when deciding the mode of birth. The key issues to include in the discussion are listed below under specific risks and benefits (see "What are the Specific Risks and Benefits of VBAC," below). (Evidence level IV)
The risks and benefits should be discussed in the context of the woman's individual circumstances, including her personal motivation and preferences to achieve vaginal birth or ERCS, her attitudes towards the risk of rare but serious adverse outcomes, her plans for future pregnancies, and her chance of a successful VBAC (principally whether she has previously had a vaginal birth; see discussion under section 6.1 in the original guideline document). In addition, where possible, there should be review of the operative notes of the previous caesarean to identify the indication, type of uterine incision, and any perioperative complications. (Evidence level IV)
What are the Contraindications to VBAC?
C - Women with a previous uterine incision other than an uncomplicated low transverse caesarean section incision who wish to consider vaginal birth should be assessed by a consultant with full access to the details of the previous surgery.
B - Women with a prior history of two uncomplicated low transverse caesarean sections, in an otherwise uncomplicated pregnancy at term, with no contraindication for vaginal birth, who have been fully informed by a consultant obstetrician, may be considered suitable for planned VBAC.
There is limited evidence on whether maternal or neonatal outcomes are significantly influenced by the number of prior caesarean births or type of prior uterine scar. Nonetheless, due to higher absolute risks of uterine rupture or unknown risks, planned VBAC is contraindicated in women with:
- Previous uterine rupture—risk of recurrent rupture is unknown
- Previous high vertical classical caesarean section (200–900/10,000 risk of uterine rupture) where the uterine incision has involved the whole length of the uterine corpus
- Three or more previous caesarean deliveries (reliable estimate of risks of rupture unknown). (Evidence level IIb, III, and IV)
However, it is recognised that, in certain extreme circumstances (such as miscarriage, intrauterine fetal death) for some women in the above groups, the vaginal route (although risky) may not necessarily be contraindicated. A number of other variants are associated with an increased risk of uterine rupture. These include: women with a prior inverted T or J incision (190/10,000 rupture risk) and women with prior low vertical incision (200/10,000 rupture risk). (Evidence level IIa)
What are the Specific Risks and Benefits of VBAC?
B - Women considering the options for birth after a previous caesarean should be informed that planned VBAC carries a risk of uterine rupture of 22–74/10,000. There is virtually no risk of uterine rupture in women undergoing ERCS.
B - Women considering the options for birth after a previous caesarean should be informed that planned VBAC compared with ERCS carries around 1% additional risk of either blood transfusion or endometritis.
B - Women considering planned VBAC should be informed that this decision carries a 2–3/10,000 additional risk of birth-related perinatal death when compared with ERCS. The absolute risk of such birth-related perinatal loss is comparable to the risk for women having their first birth.
B - Women considering the options for birth after a previous caesarean should be informed that planned VBAC carries an 8/10,000 risk of the infant developing hypoxic ischaemic encephalopathy (HIE). The effect on the long-term outcome of the infant upon experiencing HIE is unknown.
B - Women considering the options for birth after a previous caesarean should be informed that attempting VBAC probably reduces the risk that their baby will have respiratory problems after birth: rates are 2–3% with planned VBAC and 3–4% with ERCS.
B - Women considering the options for birth after a previous caesarean should be informed that the risk of anaesthetic complications is extremely low, irrespective of whether they opt for planned VBAC or ERCS.
B - Women considering the options for birth after a previous caesarean should be informed that ERCS may increase the risk of serious complications in future pregnancies.
Planned VBAC In Special Circumstances
How Should Women be Counselled in the Context of Obstetric Complications?
Preterm Birth
B - Women who are preterm and considering the options for birth after a previous caesarean should be informed that planned preterm VBAC has similar success rates to planned term VBAC but with a lower risk of uterine rupture.
Twin Gestation, Fetal Macrosomia, Short Interdelivery Interval
C - A cautious approach is advised when considering planned VBAC in women with twin gestation, fetal macrosomia, and short interdelivery interval, as there is uncertainty in the safety and efficacy of planned VBAC in such situations.
Intrapartum Support and Intervention During Planned VBAC
Where and How Should VBAC be Conducted?
B - Women should be advised that planned VBAC should be conducted in a suitably staffed and equipped delivery suite, with continuous intrapartum care and monitoring and available resources for immediate caesarean section and advanced neonatal resuscitation.
Obstetric, midwifery, anaesthetic, operating theatre, neonatal and haematological support should be continuously available throughout planned VBAC and ERCS. (Evidence level IV)
C - Epidural anaesthesia is not contraindicated in planned VBAC.
B - Women should be advised to have continuous electronic fetal monitoring following the onset of uterine contractions for the duration of planned VBAC.
Early diagnosis of uterine scar rupture followed by expeditious laparotomy and resuscitation is essential to reduce associated morbidity and mortality in mother and infant. There is no single pathognomic clinical feature that is indicative of uterine rupture but the presence of any of the following peripartum should raise the concern of the possibility of this event:
- Abnormal cardiotocograph (CTG)
- Severe abdominal pain, especially if persisting between contractions
- Chest pain or shoulder tip pain, sudden onset of shortness of breath
- Acute onset scar tenderness
- Abnormal vaginal bleeding or haematuria
- Cessation of previously efficient uterine activity
- Maternal tachycardia, hypotension, or shock
- Loss of station of the presenting part
The diagnosis is ultimately confirmed at emergency caesarean section or postpartum laparotomy. (Evidence levels III, IV)
Induction and Augmentation
How Should Women with a Previous Caesarean Birth Be Advised in Relation to Induction of Labour or Augmentation?
B - Women should be informed of the two- to three-fold increased risk of uterine rupture and around 1.5-fold increased risk of caesarean section in induced and/or augmented labours compared with spontaneous labours.
The additional risks in augmented VBAC mean that:
- Although augmentation is not contraindicated it should only be preceded by careful obstetric assessment, maternal counselling, and by a consultant-led decision.
- Oxytocin augmentation should be titrated such that it should not exceed the maximum rate of contractions of four in 10 minutes; the ideal contraction frequency would be three to four in 10 minutes.
- Careful serial cervical assessments, preferably by the same person, are necessary to show adequate cervicometric progress, thereby allowing augmentation to continue.
The intervals for serial vaginal examination and the selected parameters of progress that would necessitate discontinuing VBAC labour should be consultant-led decisions.
When informing a woman about induction (prostaglandin or non-prostaglandin methods) and/or augmentation, clear information should be provided on all potential risks and benefits of such a decision and how this may impact on her long-term health. For example, women who are contemplating future pregnancies may accept the short-term additional risks associated with induction and/or augmentation in view of the reduced risk of serious complications in future pregnancies if they have a successful VBAC. (Evidence level IV)
Definitions:
Grading of Recommendations
Grade A - Requires at least one randomised controlled trial as part of a body of literature of overall good quality and consistency addressing the specific recommendation. (Evidence levels Ia, Ib)
Grade B - Requires the availability of well controlled clinical studies but no randomised clinical trials on the topic of recommendations. (Evidence levels IIa, IIb, III)
Grade C - Requires evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities. Indicates an absence of directly applicable clinical studies of good quality. (Evidence level IV)
Levels of Evidence
Ia: Evidence obtained from meta-analyses of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well-designed controlled study without randomisation
IIb: Evidence obtained from at least one other type of well-designed quasi-experimental study
III: Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies, and case studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
