Written by Astrid Osbourne

Reproduced with the kind and direct permission of author Astrid Osbourne for IWMM. This material is © A Osbourne and as such should not be reproduced either online or in print without express permission.

Success Rates for Vaginal Birth After CS:
Success rates vary from 60% to 80%
A major consideration for successful VBAC is the reason for the first CS

A large Australian Study (1) indicates that the attitudes of Clinical staff influence women’s anxiety levels and that this may reduce the chances of a successful outcome.

A longitudinal American study in a small rural community (2) reported a success rate of 75%. This was in response to falling VBAC rates in the USA. They report that repeat elective CS accounts for one third of the annual rate.
Fewer women who went to CS from a failed trial of labour had operative complications when compared with women who went to elective CS.

Predicting outcomes for VBAC will be discussed in this paper.

Disadvantages of Repeat Elective CS:
There is evidence of increased operative complications (2.3), both for Mother and baby. However, for some women the likelihood of successful VBAC is reduced and labour trial risks then out weigh the risk of increased complications. For example if the first CS was for suspected cephlo-pelvic disproportion.

Trial of Labour after more than one CS – a study in the Netherlands (4) measured outcomes for women with two or three previous CS. Their conclusions were that for selected women a trial of labour can be a safe option but there are increased risks for women with more than one uterine scar.

Disadvantages of Vaginal Birth after CS:
The greatest perceived risk is from uterine scar rupture.
Uterine rupture is a relatively rare occurrence. A literature review of scar rupture published in 2003 (5) states that the first problem in interpreting the literature is that scar rupture is defined in different ways in different studies.
a) Scar rupture is usually defined as symptomatic scar separation that requires surgical intervention.
b) In some studies scar dehiscence is defined as asymptomatic scar separation or thinning that does not require intervention.
c) Some studies group these occurrences together.

0.5% is the most widely quoted risk rate for uterine scar rupture during VBAC. Women who elect to have repeat CS are not without risk of scar rupture, rates of 0.03% -0.2% are quoted.

The characteristics of the previous CS are very important when calculating increased risk factors. They are:

a) Type of scar – single layer or double layer closure of the uterus.
b) Number of previous CS.
c) Number of subsequent vaginal births.
d) Inter-birth interval.
e) Post surgery Infection.
f) Reason for CS.

Concerns within this pregnancy – placenta position and the size of the baby.

Prediction of success for VBAC:
Some factors will influence the success of a VBAC. This paper has listed the results of the latest studies that are attempting to analyse these factors.

Two recent studies have tested formulae for predicting outcome of VBAC (6.7). The main aim of these studies is to help women and practitioners to understand the main factors for failure and success.
In this study (6) groups of VBAC births were compared with failed trial of labour, the key factors for failed VBAC were:

a) Women were heavier [BMI increased].
b) More women in the successful group had a vaginal birth before.
c) More successful VBAC with spontaneous labour.
d) More success when cervical dilatation is 3cms or more on admission.
e) More success when the presenting part is low on admission.

Factors that were the same in both groups – Birth weight, nationality & ethnicity, incidence of antenatal care.

The study used assessment scoring tools by Troyer and Parisi, Alamia et al and Flamm and Geiger.
Study (7) looked at Induction of VBAC labour. All the women in the study had one previous CS. They found:

Factors associated with failed VBAC:
a) Diabetes, pre-existing or gestational.
b) Previous CS for failure to progress in labour.
c) None effacement [ripening of the cervix] of the cervix.
d) Induction past the due date.

A 2003 study (8) looked at the weight of women who under went trial of VBAC labour. This study found that women under 200 pounds had the best success, followed by women who were 200-300 pounds. Women who were categorised as morbidly obese [over 300lbs] had the least VBAC success.

Birth Weight and VBAC – this study (9) looked at the possible effect of success and morbidity when babies are large.
Success for VBAC decreased with increased birth weight, particularly over 4000gms when the VBAC rate falls below 50% for women who have not had a previous vaginal birth. There were significant results for VBAC failure when women were augmented in labour or induced. This study urges that family birth histories should be a useful indicator for success for women who’s family have larger babies.

Number of prior CS operations:
There are studies where there has been no significant difference in uterine scar rupture for women who have had more than one CS. However, the numbers of women who can be studied are very small and this may be the reason for this result.
O’Brien (5) has cited a retrospective American study that draws attention to the largest study, the results become more reliable when 12,707 women are included in the study. Uterine scar rupture occurred at a rate of 1% in the two scar group and at a rate of 0.5% in the single scar group. However, this study did not identify any other risk factors that may have increased the risk of scar rupture.

Prior Vaginal Birth:
Prior vaginal birth either before the incidence of CS or after, has a protective influence with regard to scar rupture (5). Zelop et al (10) measured the effect of prior vaginal birth on the risk of uterine scar rupture in 3,783 women. The rate of rupture for women with a prior vaginal birth was 0.2% compared with 1.1% for women with no prior vaginal births.

Predicting VBAC: A review of Screening Tools
There is little high quality data to help to identify factors and guide clinical decisions about who will achieve a successful VBAC.
Screening tools rely on the woman’s past history as an indicator for this pregnancy and birth.
An overview of 7 unvalidated screening/scoring tools came to these conclusions (12):

Finally it is important that women are well informed and part of the decision making process with regard to their VBAC care, as this lowers anxiety levels and raises confidence.

Maternal Request for Repeat CS and the Importance of Individualised Care:
The Netherlands lead the world with their low CS rates and a trial for VBAC rate of 73% in contrast to Brazil where the CS rate is 75% and VBAC virtually unheard of. In the UK trends develop from hospital to hospital and from region to region. However, it is important to have the opportunity to explore ALL options and ALL risks as Vaginal Birth is acknowledged as an option for women after CS.
ÿ Childbirth with or without a uterine scar is not risk fee.
ÿ It is important to assess your individual chances of success; as a previous CS Mother, your past history is the most important factor for consideration.

It is equally important to discuss your emotions, anxieties and wishes for your birth. Many VBAC women need to examine the reasons and circumstances for the previous CS birth. Some women do not wish to take up conventional labour ward care, this must be discussed and alternatives understood with both the midwife and the obstetrician who are providing care.

Care of Women in VBAC Trial of Scar Labour:
Care falls into two categories; Mother and Baby.

Mother:
The care of the labouring VBAC woman is centred on the performance of the scarred uterus. There should be close midwifery attention through out, contractions must be observed and measured and compared with the rate of dilatation of the cervix and the descent of the baby in the pelvis. VBAC women are monitored more closely because of the increased risk of uterine rupture.
Blood pressure measurement and more importantly the pulse rate should be performed regularly [pulse every 15mins (5)].

Many hospitals and Obstetricians support the use of epidural analgesia.

All labour care that is useful to women with no uterine scar will also apply, for example movement, support and upright postures.

Baby:
The National Institute for Clinical Excellence recommend that VBAC women should have their baby continuously electronically monitored during labour. However, the guideline also recommends that personal preferences are taken into account when planning care.
It is expected that uterine rupture will distress the baby before the Mother is aware of other signs occurring and that the easiest and quickest way to see an affect, is by a continuous readout of the baby’s heart rate.
There are no studies that have scientifically compared continuous monitoring with intermittent monitoring in spontaneous full term VBAC labour. However, there are outcome time studies that suggest that the response time during uterine scar rupture is crucial for the baby (5. 11). Babies born within 17mins of any sign of rupture did best in one study. The absolute risk of perinantal death (11) associated with VBAC is very small and is similar to that expected of first time babies at full term in normal labour.

It is fair to mention that in a review of the literature concerning action time, O’Brien (5) found that immediate action in institutions that were well equipped did not always result in the baby being unaffected.

Induction of Labour:
Labour may be induced for two main reasons; the pregnancy progresses beyond term and the presence of a medical reason to induce.

It is recommended that careful consideration be made when induction becomes an option for VBAC women.
The is a lot of research evidence about VBAC induced labour and drug accelerated labour. Work by Zelop et al (10) found that induction with prostin E2 conferred a 4.6 fold increased risk of uterine rupture. Augmented labour showed an increased risk for VBAC women, however, others factors such as birth weight may have been contributory. The use of Misoprostol [prostaglandin E1] has been discouraged after trials that increased the risk of uterine scar rupture (5. 11).

When the need for Induction of labour becomes probable for a woman with a uterine scar, a detailed discussion with her Obstetrician is necessary. Some women may choose to go directly to repeat CS when discussion takes place.

Care of VBAC women at home or in a birth centre:
VBAC care in a well equipped traditional labour ward is considered to be the safest place for both Mother and Baby, though no guarantee can ever be given to a Mother with regard to absolute outcome. However, Obstetricians and Midwives acknowledge that this style of care can be emotionally harrowing for women who have suffered a poor birth experience in the past.
There are no research trials that compare total midwifery care with our traditional methods of labour ward care (13). A retrospective study of midwifery care in an American hospital reports similar results to Obstetric driven care. However, all the women were continuously electronically monitored {EFM}. Home and Birth centre care does not include EFM.
Water birth requests by VBAC women has become more common, again there is no scientific research to support this. An audit of VBAC water births by Garland and Crooke (14) demonstrates that success is possible and can be achieved with realistic risk assessment.

University College London Hospital is committed to birth planning VBAC women in a sensitive and accommodating fashion. It is our aim that Midwives, Obstetricians and women desiring VBAC work together to find the care solution that best accommodates the needs and wishes of the woman and her family. In this situation all the factors should be discussed and an agreed care plan written prior to labour beginning.

The Bloomsbury Birth Center opened in April 2003. In the first year 10 VBAC women booked for labour and birth care in the BBC. 5 were successful, of which 2 had water births, 5 resulted in repeat CS. By comparison the Labour ward has a higher VBAC success rate.

References:
1. 2000. Appleton. B., Targett. C., Rasmussen. M., Readman. E., Sale. F., Permezel. M., and the VBAC Study Group. Knowledge and Attitudes about vaginal birth after CS in Australian Hospitals. Australian and New Zealand Journal of Obstetrics and Gynaecology.: 40.2: 195-199.
2. 2003. Upadhyaya. C.D., Upadhyaya. D.M. and Carlan. S.J. Vaginal Birth After Caesarean Delivery in a Small Rural Community with a Solo Practice. American Journal of Perinatology. 20. 2. 63-67.

2. 2003. Mankuta. D.D., Leshno. M.M., Menasche. M.M. and Brezis. M.M. Vaginal Birth after CS: Trial of labour or repeat CS? A decision analysis. American Journal of Obs & Gynae. Sept. 714-719.

3. 2003. Spanns. W.A., van der Vliet. L.M.E., Roell-Schorer. E.A.M., Bleker. O.P. and van Roosmalan. J. Trial of Labour after two or three previous CS. European Journal of Obs & Gynae & Reproductive Biology. 110. 16-19.

4. 2003. O’Brien-Abel. N. Uterine Rupture During VBAC Trial of Labour: Risk Factors and Fetal Response. Journal of Midwifery and Women’s Health. 1526-9523.

5. 2004. Dinsmoor. M.J. and Brock. E.L. Predicting Failed Frial of Labour After Primary Caesarean Delivery. American College of Obs and Gynae. 103.2. 534-538.

6. 2004. Grinstead. J. and Grobman. W.A. Induction of Labour After One Prior Caesarean: Predictors of Vaginal Delivery. American College of Obs & Gynae. 103.2. 282-286.

7. 2003. Carroll. C.S., Magann. E.F., Chauhan. S.P., Klauser. C.K. and Morrison. J.C. Vaginal birth after CS versus elective repeat CS: Weight-based outcomes. American Journal of Obs & Gynae. 188.1516-22.

8. 2003. Elkousy. M.A., Sammel. M., Stevens. E., Pierpet. J.F. and Macones. G. The effect of birth weight on vaginal birth after Caesarean delivery success rates. American Journal of Obs & Gynae. 188.3 824-830.

9. 2000. Zelop. C.M., Shipp. T.D., Repke. J.T., Cohen. A., Leiberman. E. Cited by O’Brien-Abel. N. 2003. Uterine Rupture During VBAC Trial of Labour: Risk Factors and Fetal Response. Journal of Midwifery and Women’s Health. 1506-9523.

10. 2003. Biswas. A. Management of Previous Caesarean Section. Current Opinion in Obs & Gynae. 15:123-129.

11. 2004. Hashima. J.M., Eden. K.B., Osterweil. P., Nygren. P. and Guise. J.M. Predicting vaginal birth after caesarean: A review of prognostic factors and screening tools. American Journal of Obstetrics and Gynaecology. 190. 547-55.

12. 2004. Avery. M.D., Carr. C.A. and Burkhardt. P. Vaginal Birth after CS: A Pilot Study of Outcomes in Women Receiving Midwifery Care. Journal of Midwifery and Women’s Health. 113-117.

13. 2004. Garland.D. and Crook. S. Is the use of water in labour an option for women following a previous LSCS? MIDIRS 14:1. 63-67.

This paper has been prepared by:
Astrid Osbourne. Consultant Midwife. 3/10/04
Review: November 2005.