VBAC

VAGINAL BIRTH AFTER PREVIOUS CAESAREAN SECTION ('VBAC')

These guidelines outline agreed regional management for trial for vaginal birth after one previous lower segment Caesarean section (LSCS). Management of individual cases may vary and should be discussed with Consultant.

Background

With a history of one previous delivery by LSCS, the majority of women are suitable for a trial for VBAC in a subsequent pregnancy. The chance of successful vaginal delivery is between 70 - 80%. The incidence of "scar dehiscence" (opening of the scar without serious maternal or fetal consequence) is approximately 0.5% (1 in 200) but the incidence of "scar rupture" (with potential serious fetal or maternal consequences) is lower at 0.1% (1 in 1000)(1). The need for hysterectomy is rare (1). Cautious use of oxytocin augmentation in spontaneous labour is not associated with an increased risk of dehiscence or rupture [OR1.2 (95%CI 0.7-2.1)] (2). However, induced labour, particularly with prostaglandin carries an increased risk of dehiscence or rupture (1,3). These guidelines cover three specific areas:

1. Antenatal management and counselling
2. Induction of labour in cases of VBAC
3. Management of labour for VBAC

Antenatal Counselling

Review old notes pertinent to the previous LSCS - directly or by correspondence with other hospital
Initial discussion with patient (review the labour that resulted in LSCS; discuss outcomes for VBAC - unit specific; offer appropriate information leaflet; plan VBAC for majority)
Record final agreed plan for delivery in antenatal record (Consultant should be involved in this decision) - this may be nearer term.

Induction of Labour in cases of VBAC

The risk of uterine rupture is increased in induced labour compared to spontaneous labour and this increase is more marked if both prostaglandin (PG) and oxytocin are used (3).

Therefore:
a) Induction of labour should only be undertaken for valid obstetric indications
b) Offer membrane sweep at 41 weeks
c) The preferred method of induction is by forewater amniotomy (ARM) with judicious oxytocin augmentation (as per unit protocol)
d) PG priming should be kept to a mimimum - an experienced obstetrician should assess the need for PG. If PG is necessary, ONE 3mg PG intravaginal tablet only should be used and must be administered on the delivery suite or high dependency area(4). Further doses of PG should only be used after discussion with Consultant.
e) Oxytocin infusion should not be started for 6 hours following PG administration (4). The maximum dose should not exceed 32 mU/min (4).

Management of Labour for VBAC

ONSET	Amniotomy (ARM)	- should be considered when the cervix is 3cm dilated
	IV access	- insert 16G 'Venflon' at the start of labour and take relevant blood tests via cannula before 'Hepsal' and capping
	Blood tests	- Group & Save (plus Hb if indicated)
	SpR	- to be informed after initial assessment by midwife
FIRST STAGE	FH monitoring	- continuous electronic FH monitoring throughout labour
	Progress	- expect normal progress (ie cervical dilatation of at least 1cm/hour from 3cm dilatation). If progress is less than this - experienced obstetrician to review
	Vaginal examination	- 4 hourly up to 7cm dilatation & 2 hourly thereafter: if progress is less than 1 cm/hour, an experienced obsterician must assess and discuss progress with consultant
	Augmentation	- use agreed unit syntocinon regimen: do not exceed 32mU/min (4)
SECOND STAGE	Length	- with epidural, if maternal and fetal condition are good and vertex is not low cavity, allow a maximum of 1 hour for 'passive' descent - consider assistance if spontaneous delivery is not imminent after 1 hour of active pushing (or as otherwise indicated)
	Forceps/ventouse	- unless the vertex is on or near the perineum (ie low cavity; 2-3cm below spines): a) SpR to examine - and discuss with Consultant before proceeding b) consider trial of forceps/ventouse in theatre
THIRD STAGE	Uterine scar	- the integrity of the uterine scar does not need to be checked routinely - D/W consultant if: a) there is persistent or excessive vaginal bleeding post-delivery or b) if there are concerns about scar integrity

Special Points

Length of labour (VBAC)	- inform consultant when appropriate oxytocin augmentation does not correct progress of labour. This review and discussion should be done earlier rather than later (5).
Intrauterine pressure (IUP) monitoring	- routine use of IUP does not improve obstetric outcome (6) or reduce scar rupture rate. - if available, consider IUP in oxytocinon-augmented labour when contractions are difficult to assess or monitor (eg obese patients) - using the 'active contraction area' per 15 minutes - aim for pressures near to the mean pressure in normal labour = 1099 kPas/15 mins (7). [Normal range = 700 - 1500 kPas/15 mins (10th - 90th centiles)].
Scar dehiscence & rupture	Symptoms and signs of impending rupture include: * rising maternal pulse rate (MAY BE THE ONLY SIGN) * acute fetal heart rate abnormalities * sudden cessation of contractions * continuous scar pain (still occurs with epidural) * vaginal bleeding * haematuria * retraction of presenting part (on vaginal assessment) - ALL STAFF must be aware of these symptoms & signs - they may occur for the first time in the SECOND STAGE
Subsequent labours	- the scar rupture rate does not decrease with each subsequent labour: women with a previous LSCS should have ALL subsequent labours managed as described above.

References

1. Society of Obstetricians and Gynaecologists of Canada. Vaginal birth after previous Caesarean birth. Clinical Practice Guidelines No 68, December 1997. J Soc Obstet Gynaecol Can 1997; 19: 1425-28.

2. Rosen GM, Dickinson JC, Westhoff CL. Vaginal birth after Cesarean: a meta-analysis of morbidity and mortality. Obstet Gynecol 1991; 77: 465-70.

3. Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. Risk of uterine rupture during labor among women with a prior Cesarean section. NEJM 2001; 345(1): 3-8

4. Induction of labour - NICE Inherited Guideline D. National Institute for Clinical Excellence, London, 2001.

5. Turner MJ. Uterine rupture. In: Operative Delivery and intrapartum surgery. Clinical obstetrics & gynaecology - best practice and research. Baskett T, Arulkumaran S (Eds). Bailliere-Tindall, London, 2002. 16(1): 69-79.

6. Chua S, Kurup A, Arulkumaran S, Ratnam SS. Augmentation of labour: does internal tocography result in better obstetric outcome than external tocography? Obstet Gynecol 1990; 76:164-7.

7. Steer PJ, Carter MC, Beard RW. Normal levels of active contraction area in spontaneous labour. Br J Obstet
Gynaecol 1984; 91:211.

K HINSHAW (on behalf of M&FM Special Interest Group) - May 2003

Please e-mail - kim.hinshaw@lineone.net with any queries

Mr Kim Hinshaw MRCOG
Consultant Obstetrician & Gynaecologist
Sunderland Royal Hospital
Tyne & Wear
SR4 7TP