VBAC and Uterine Rupture

What is the risk of uterine rupture in a Vaginal Birth After Caesarean (VBAC)?

There are two types of event which are sometimes lumped together as 'uterine rupture'.

The first, and most common, is a 'dehiscence'. This is where the scar starts to undo, but only by a small amount; neither mother or baby are affected. These are often called 'asymptomatic' ruptures as no symptoms are shown by mother or baby - nobody is hurt.

The dehiscence is noticed only where a repeat caesarean is performed for reasons apart from symptoms of uterine rupture, or when there is a manual exploration of the uterus after VBAC. This means that the doctor puts her hand into the uterus and feels for tears. Such explorations are not routinely done nowadays because of risk of discomfort and infection for the mother, so many dehiscences could pass unnoticed if the mother has a VBAC.

True uterine rupture is symptomatic, which means that the mother is losing enough blood for her and the baby to be affected. Her blood pressure falls, her pulse changes, she may experience abnormal pain in one area, even through an epidural. The baby goes into distress as its oxygen supply is interrupted. This situation is extremely dangerous for the baby and for the mother, and the baby must be delivered urgently by caesarean if it is to live.

Rates of rupture and dehiscence are lowest for 'lower-segment' caesarean sections, sometimes abbreviated to LSCS. This means that the cut was made across the bottom part of the womb, which is the usual approach. 'Classical' caesareans involve a vertical cut and carry a higher risk of rupture.

True rupture occurs in between 0.3 and 0.7% of VBAC labours, depending on which study you look at [1, 2]. The working estimate that many people use is 0.5%. Dehiscences are thought to occur in around 1.1% of VBAC labours.

Let's look at the mother's chances of needing an immediate emergency caesarean. 'Immediate' means the baby has to be delivered right now, as opposed to the standard definition of 'emergency' caesarean - which just means one that was not planned when labour started.

'A Guide to Effective Care in Pregnancy and Childbirth', which is a well-respected summary of evidence-based practice, says that the rate of reported uterine rupture has ranged from 0.09% to 0.8% for women with a single baby, head-down, who planned a vaginal birth after one previous lower-segment caesarean. The authors comment:

"To put these rates into perspective, the probability of requireing an emergency cesarean section for acute other conditions (fetal distress, cord prolapse, or antepartum hemorrhage) in any woman giving birth, is approximately 2.7%, or up to 30 times as high as the risk of uterine rupture with a planned vaginal birth after cesarean"

So once a mother has had a past caesarean, her risk of needing emergency caesarean in future rises from around 2.7% to around 3.2%. Even taking higher figures for uterine rupture, she is still more than five times more likely to need a true emergency caesarean for other reasons, than for uterine rupture.

Uterine Rupture and Induction of Labour

Induction of labour using oxytocin (pitocin, syntocinon) and prostaglandins (eg prostaglandin gel, prostin) have been associated with increased risk of uterine rupture. Misoprostol (Cytotec) has been associated with a greatly increased risk of rupture. These drugs and studies on them are discussed on the pages on VBAC and Induction.

What are the warning signs of uterine rupture?

The first warning signs of uterine rupture are usually changes in the baby's heart rate. The studies on signs of uterine rupture mention 'prolonged fetal heart rate decelerations', 'variable decelerations' and 'fetal bradycardia'. The reason that VBAC births in hospitals are generally continuously monitored is to detect such heart rate changes as soon as they occur.

However, note that hospital birth and continuous monitoring is no guarantee that these signs will be noted or acted upon, although we would always hope that they were. For a tragic story of a hospital VBAC in which these signs were not acted upon for several hours, leading to the death of the baby, see Catherine Grace's story. Another example of a hospital VBAC where warning signs were ignored - the mother suffered abnormal pain as her uterus was ripping - can be read in Kim's story at birthstories.com. This baby survived, but sadly was left with brain damage.

If the mothers in these two cases had continuous attention from a midwife or doctor who was knowledgeable about VBACs, the outcome would almost certainly have been different, whether the birth was planned for home or hospital.

Reducing the Risk of Rupture

Some women are at higher risk of uterine rupture than others; not all VBAC attempts are equally safe.

Induction of labour

Research suggests that women whose labours are induced with prostaglandin gel (eg Prostin), or oxytocin (Pitocin, Syntocinon) are at higher risk of rupture. Women whose labours are induced with Cytotec (Misoprostol) are at greatly increased risk of rupture. Conversely, if you refuse these drugs in labour then your risk of uterine rupture is reduced. Of course, there are disadvantages to refusing such drugs; it may mean that you choose an elective caesarean, or continue the pregnancy well beyond term, for example, or if your labour is slow, you may be faced with a choice between simply waiting it out, or having a caesarean.

Already had a VBAC?

Women who have already had one vaginal birth after caesarean appear to be at less risk of suffering a rupture during future labours, than women who are attempting their first VBAC [4]. This is significant as women who have already had one VBAC are sometimes worried that their scar will have been put under stress by the first labour, and so might be weaker next time around. So, if you have already had one vaginal birth following your caesarean, you are in a lower-risk category for rupture than a woman whose scar has not been 'tested' by labour.

Assisted Deliveries

Instrumental deliveries (forceps or ventouse) are known to increase the risk of uterine rupture in women with caesarean scars - see [4] below, but further references for this are available and will be added later.

Sources of more information

Women's experiences of uterine rupture - stories which need to be told.

Catherine Grace's parents have collected a great deal of research on VBAC and they suggest a list of questions to ask your doctor or midwife when planning a VBAC, and although this assumes that the birth will occur in hospital, it is worth a look whatever your plans.

Good, plain English article on uterine rupture: www.birthrites.edsite.com.au/uterinerupt.html

An overview of uterine rupture, signs, and management, is at Obgynmanagement.com
(www.obgynmanagement.com/07_00/postpartum.html ).

Uterine Rupture Support Group Email support group specifically for women who have had a uterine rupture.
http://groups.yahoo.com/group/AUterineRuptureSupportgroup

Uterine Rupture and VBAC email group, for mothers who have experienced uterine rupture, for women considering VBAC, and for health professionals who have an interest in the subject.
http://groups.yahoo.com/group/Uterinerupture.

West Midlands Perinatal Institute practice recommendations for uterine rupture
www.wmpi.net/reviews/oe/oe_uterine_scar_rupture.htm

References

[1] Vause and Macintosh
Use of prostaglandins to induce labour in women with a caesarean section scar
BMJ 1999;318:1056-1058 ( 17 April )

[2] Miller DA; Diaz FG; Paul RH.
Vaginal birth after cesarean: a 10-year experience.
Obstet Gynecol 1994 Aug; 84:255-8
Over 17,000 women having VBACs, the uterine dehiscence rate was 1.1% and symptomatic rupture occured in 0.7% of labours.

[3] 'A Guide to Effective Care in Pregnancy and Childbirth' 3rd edition, by Enkin, Kirse et al, Oxford University Press, 2000 (p368)

[4] "Successful first vaginal birth after cesarean section: a predictor of reduced risk for uterine rupture in subsequent deliveries."
Shimonovitz S, Botosneano A, Hochner-Celnikier D
Isr Med Assoc J 2000 Jul;2(7):526-8

"CONCLUSIONS: Once a woman has achieved VBAC the risk of rupture falls dramatically. The use of oxytocin, PGE2 and instrumental deliveries are additional risk factors for rupture, therefore caution should be exerted regarding their application in the presence of a uterine scar, particularly in the first vaginal birth after cesarean." Medline Abstract

This page last updated 16 November 2002

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