Caesarean delivery rates are increasing throughout the world and exceed 30% in many Western countries. If current trends continue, rates may top 50% in the next 20 years. This prompted us to invite original manuscripts and reviews for a themed issue of BJOG dedicated to birth following caesarean delivery. We hoped to address both short-term and long-term implications of caesarean delivery and to generate discussion about possible remedies to the dramatic increase in caesareans. We were pleasantly surprised by the response.
Vaginal birth after caesarean section
The biggest part of this themed issue deals with vaginal birth after caesarean (VBAC) or trial of labour after caesarean (TOLAC). On page 183 Knight et al., using NHS data, report on the factors associated with the uptake and success of VBAC in England. They used the data from the Hospital Episode Statistics and identified 143 970 women with a history of previous caesarean section who gave birth over a 12-month period between 2011 and 2012. Overall, just over half of them attempted TOLAC and two-thirds had a VBAC. They found that TOLAC following a planned caesarean is associated with increased success, and that success rates are lower if the primary caesarean was performed for failed induction. The group also report results on the rate of VBAC success by ethnicity (Figure 1).
Typically, the general chance of success quoted by obstetricians to women considering an attempt at VBAC is two-thirds, but is it possible to predict an individualised rate of success? Several prediction models have been published, but none have been established in a European population. Schoorel et al. have validated one such prediction model to estimate individualised success rates for attempted VBAC on page 202. The same group of researchers also developed and pilot tested a patient decision aid for individualised prediction of success. They expect the patient decision aid to improve the quality of decision-making but this remains difficult to prove or disprove. Women with a low probability of success may not wish to try at all. On the other hand, those who had been reluctant for TOLAC may be encouraged by a high chance of success.
Many questions on VBAC remain unanswered. How should the utility of prediction models be assessed and will this alter the overall caesarean rate? It is ideal for the health system that those women with predicted high success rates for VBAC try (and the majority succeed), whereas those with low predicted success rates do not try (and so save resources). From a public health point of view, this is an optimal use of resources. However, data from prediction models need to be reconciled with patient choices and expectations. Many women have strong feelings about TOLAC, regardless of their probability of success.
Safety of VBAC
The fact that caesarean delivery is a relatively safe procedure is a major reason for rising caesarean delivery rates. There was a time, not long ago, when accidental caesarean by bull-horn injury was safer than surgeons performing it. With the development of antibiotics, blood transfusion, anaesthesiology and better surgical techniques, the procedure has become increasingly safe and is used more and more readily. The commentary by Wanyonyi et al. on page 141 uses this argument to propose that in rural sub-Saharan Africa, a repeat caesarean should be performed more often, because it is safer than TOLAC. On the other hand, as argued by Boulvain on page 144, the cumulative effect of many caesareans cannot be easily denied. Scott gives us valuable practical advice on the intrapartum management of women undergoing TOLAC (page 157), and Dexter et al. discuss maternal choice in mode of delivery following a previous caesarean from a legal perspective (page 133). Increased awareness of the long-term complications of caesarean delivery may ultimately impact the medico-legal influence that has contributed to the increased rate of caesareans.
Implications of caesarean birth on the next pregnancy
Although data have been mixed, several studies have reported that the risk of stillbirth is higher following a previous caesarean birth compared with previous vaginal birth. What could be the pathological mechanism behind this dramatic complication? On page 210 , Flo et al. show that uterine artery volume blood flow and the fraction of maternal cardiac output distributed to the uteroplacental circulation are lower, and uterine vascular resistance is higher, in women with previous caesarean section compared with those without. This suggests that a deficient blood supply to the scarred uterus may contribute to at least some of the stillbirths in women with a previous caesarean delivery.
Is it preferable to undergo a planned caesarean delivery before the onset of labour or an emergency intrapartum caesarean during a ‘failed’ VBAC attempt? Kok et al. investigated this question using a nationwide review of over 40 000 women in their second pregnancy after undergoing a caesarean delivery in the first one (page 216). They found that the risk of stillbirth and postpartum haemorrhage was higher in the second birth following a planned rather than an intrapartum caesarean section. This study shows that in some cases, attempting a vaginal birth is better, even if it does not succeed and an ‘emergency’ caesarean is required. Another large Swedish study in this issue reports that the risk of retained placenta is higher following a successful VBAC compared with previous vaginal birth with an odds ratio of 1.45 (95% CI 1.32–1.59). This observation is important for clinicians performing VBAC, who should be on the alert for retained placenta. The legal review by Jauniaux and Khan indicates the need for obstetricians to provide women considering VBAC with a detailed description of the risks and the fact that there may be a need to transform the VBAC into a caesarean delivery if the labour does not progress as expected and/or symptoms of uterine rupture appear during labour.
Prior caesarean section and placenta accreta
Perhaps the most worrisome long-term morbidity of caesarean delivery is the risk of placenta accreta in subsequent pregnancies. The fact that the first detailed description of a placenta accreta happened within a couple of decades of major changes in caesarean surgical techniques is highly suggestive of a direct relationship between previous uterine surgery and abnormal placental adherence. Placenta accreta is now a well-recognised long-term severe complication of caesarean delivery and its incidence is increasing following the increase in caesarean rates over the last two decades. A planned peripartum caesarean section–hysterectomy in cases of placenta accreta does not allow for fertility preservation. The review by Drs Wright and Perez-Delboy and the accompanying mini-commentary by Gupta (pages 163–170) describe the difficulties of and possible solutions to operative management of placenta accreta. Within this context, an accurate prenatal diagnosis of placenta accreta is pivotal. The review by Comstock and Bronsteen addresses this issue and, in particular, the contribution of magnetic resonance imaging (page 171 ). In the accompanying mini-commentary, El-Refaey et al. make a plea for screening for this dangerous condition in the first trimester using ultrasound and for research to understand its natural history.
Prior caesarean section and gynaecological problems
Recently, there is increasing evidence suggesting that a caesarean scar may not heal well, resulting in a uterine wall defect also called a ‘niche’ that can be identified by ultrasound within weeks after surgery. Van der Voet et al. have studied the prevalence of niches in caesarean delivery 6–12 weeks after the operation using transvaginal ultrasound and gel-instillation sono-hysterography. They found that postmenstrual spotting is more prevalent in women with a niche and in women with a residual myometrium <50% of the adjacent myometrium. Van der Voet et al. also present a systematic review on minimally invasive therapy for the symptoms related to scar niche indicating that scar repair reduces abnormal uterine bleeding. However, evidence is insufficient to show an impact on subsequent fertility and pregnancy outcome. There is a need for more studies on uterine scar and short-term and long-term gynaecological complications and pregnancy outcome. Evidence from randomised controlled trials to evaluate the impact of surgical repair is necessary before offering this approach to women.
This themed issue covers many important aspects of caesarean delivery and its impact on women's health. Clinicians should be alerted to ways to make TOLAC and VBAC more successful and safer and to reduce some of the long-term complications of caesarean delivery. There is no doubt that modern caesarean delivery has saved the lives of countless mothers and their babies over the last century. On the other hand, the rapid increase in the rates of this procedure and its short-term and long-term medical, social and physiological complications have become a global health issue. As doctors, our primary role is not necessarily to reduce the caesarean rate, but to do our best for the welfare of women and children. However, if the increasing caesarean rate does not translate into better outcomes for mothers and babies, it would be in direct conflict with the Hippocratic oath: first of all, do no harm.
As with many things in medicine, there is a ‘happy medium’ with regard to the optimal rate of caesarean sections. Further research into strategies for reducing the rate of primary caesarean delivery, addressing the non-medical factors influencing the caesarean rate and increasing the rate of TOLAC and VBAC are desperately needed.