Description of the condition

The rate of caesarean section in high‐income countries is increasing, accounting for 23.7% of all births in the United Kingdom, 26% in Ireland (OECD Health Data 2011), and 32.8% in the United States (Hamilton 2012). Reported rates from South America are higher, reaching over 50% in private hospitals in Chile, Argentina, Brazil and Paraguay (Belizan 1999). Suggested reasons for the high proportion of caesarean births over the last few decades have included medicolegal issues, the increasing use of electronic fetal heart rate monitoring, and reduced training in operative vaginal and vaginal breech births (Mastrobattista 1999). Repeat caesarean section is the most common primary obstetric indication for repeat caesarean in 28% of births in the United Kingdom (RCOG 2001) and 32.8% of births in the United States (CDC 2010).

Concerns about the increasing caesarean section rate resulted in a consensus statement by the American College of Obstetricians and Gynecologists, that "most women with one previous caesarean delivery with a low‐transverse incision are candidates for and should be counseled about VBAC" (ACOG 2010). However, there is considerable variation in both the proportion of women attempting labour after caesarean birth (28% to 82%), as well as reported success rates (49% to 87%) (Guise 2010).

Description of the intervention

For a woman with a previous caesarean birth, the decision regarding planned mode of birth in a subsequent pregnancy will be influenced by many factors, including previous experience of a vaginal birth, desire to achieve a vaginal birth, feelings about the previous caesarean birth, and family considerations (including an easier recovery). There are benefits and harms associated with both repeat elective caesarean birth and vaginal birth after caesarean section, which will be discussed subsequently.

Repeat elective caesarean birth is associated with an increase in the risk of complications such as bleeding, the need for blood transfusion, infection, damage to the bladder and bowel, and clots in the veins of the legs (called deep venous thrombosis). As the numbers of caesarean births for each individual woman increases, so does the difficulty in performing surgery due to adhesions, and the risk of damage to the bladder or bowel at the time of surgery (Marshall 2011). There may also be difficulties in conceiving a further pregnancy or problems where the placenta develops over the scar in the uterus in a subsequent pregnancy (placenta praevia) (Marshall 2011). Occasionally the placenta may continue to develop into the muscle wall of the uterus (placenta accreta/placenta percreta). This may cause difficulties with the placenta being delivered after birth, and sometimes excessive bleeding. Babies born by caesarean may develop some difficulties with breathing (called transient tachypnoea of the newborn), and may need to spend time in a special care nursery. This is usually only for a short duration, and most babies recover fully. Occasionally a baby may develop more serious problems with his or her breathing (called respiratory distress syndrome), and may need some extra oxygen, assistance with breathing and a longer stay in the nursery. The risks of developing this relate to the use of general anaesthesia and the age at which the baby is born (Hook 1997; Morrison 1995).

One uncommon, but potentially serious complication associated with a prior uterine surgery (including a previous caesarean section), is that of uterine rupture (where the prior caesarean scar breaks down). This may occur prior to the onset of labour, or during labour while a woman is undergoing a planned vaginal birth after caesarean (VBAC). This complication can be life‐threatening for both the woman and her baby. The estimated risk of scar rupture from large prospective studies varies following VBAC from 0.2% (Crowther 2012a), to 0.7% (Landon 2004). Any vaginal birth may be associated with a non‐reassuring fetal heart rate tracing (sometimes called fetal distress) or inability of the cervix to dilate (sometimes called failure to progress or lack of progress), both of which may require birth by emergency caesarean section. Emergency caesarean birth in labour has been associated with an increased chance of infection, bleeding (increasing the need for blood transfusion), and clots in the veins of the legs (deep venous thrombosis) when compared with both vaginal birth and elective caesarean birth. Any vaginal birth may be associated with trauma to the woman's perineum (the area between the vagina and rectum) either from a tear or cut (called an episiotomy) during childbirth. Vaginal birth may also be associated with longer‐term problems for the woman, including pelvic floor weakness contributing to symptoms such as prolapse and incontinence. Infants born vaginally may have lower Apgar scores and an increased chance of trauma if the birth has been difficult, than those infants born by elective caesarean section.

How the intervention might work

In an attempt to compare the benefits and harms associated with both a planned repeat elective caesarean birth and a planned VBAC, Guise and colleagues completed a comprehensive systematic review of the literature (Guise 2010), in which the overall rates of maternal complications were low among women undergoing trial of labour and repeat caesarean birth. While the risk of hysterectomy, haemorrhage, and transfusions did not differ significantly between the two methods of birth, maternal death was increased following elective caesarean birth (13.4 per 100,000 repeat caesarean birth versus 3.8 per 100,000 for women undergoing a trial of labour) (Guise 2010). The reported rate of uterine rupture was three per 1000, and significantly higher among women who laboured (4.7/1000 trial of labour versus 0.3/1000 repeat caesarean birth).

In view of the limitations identified in these meta‐analyses and the need for more reliable information about the benefits and harms associated with both planned elective repeat caesarean birth and planned vaginal birth after caesarean, Landon (Landon 2004) and Crowther (Crowther 2012a) conducted large prospective cohort studies.

Landon and colleagues within the National Institute of Child Health and Human Development Maternal Fetal Medicine Units Network (Landon 2004) conducted a prospective observational study across 19 centres in the United States. In this study, women with any prior caesarean birth were identified from the delivery suite register, excluding those women who presented in early labour and subsequently underwent a caesarean section. A total of 33,699 women with a prior caesarean birth were involved in the study, of whom 17,898 (53.1%) attempted VBAC, and 15,801 (46.9%) underwent elective repeat caesarean section. The observed rate of symptomatic uterine scar rupture among women undergoing VBAC was 0.7% and of infant death or hypoxic ischaemic encephalopathy, 0.38%.

Crowther and colleagues (Crowther 2012a) conducted a prospective patient preference study across 14 maternity centres in Australia. In this study, women with a single prior caesarean section presenting in their next ongoing pregnancy, with a live singleton in cephalic presentation, at 37 weeks' gestation or more, and who were considered eligible to attempt planned VBAC were eligible to participate. Women were asked their preference for either planned VBAC or planned caesarean section, and assigned to their preferred study group. A total of 2323 women participated in the study. A nested randomised trial involving 22 women was conducted in parallel with the patient preference study. Fewer infants in the planned elective repeat caesarean section group suffered death or serious adverse outcome (risk ratio (RR) 0.39; 95% confidence interval (CI) 0.19 to 0.80), when compared with infants born to women in the planned VBAC group. While significantly fewer women in the planned elective repeat caesarean section group suffered major haemorrhage (RR 0.37; 95% CI 0.17 to 0.80), there were no significant differences between the two groups in risk of uterine rupture (RR0.37; 95% CI 0.04 to 3.57).

While there are risks and benefits for both planned elective repeat caesarean birth and planned vaginal birth after caesarean, current sources of information are limited to non‐randomised cohort studies, which are largely retrospective in nature, and hampered by the lack of comparability of the groups assessed. Studies designed in this way have significant potential for bias and consequently conclusions based on these results are limited in their reliability and should be interpreted with caution. As outlined by Guise and colleagues, there is little information about the outcomes of intended mode of birth, with the bulk of the available literature reporting outcomes based on actual mode of birth, with "this inception cohort the equivalent of intention to treat for randomized controlled trials" (Guise 2010).

Information from randomised controlled trials would better assess the risks and benefits of vaginal birth after caesarean section with elective repeat caesarean section in women with a previous caesarean birth.

Why it is important to do this review

Planned elective repeat caesarean section and planned vaginal birth after caesarean section for women with a prior caesarean birth are both associated with benefits and harms. Evidence for these care practices to allow women and their caregivers to make an informed decision is required.