Controversies in Obstetrics, Gynaecology and Infertility Alka Kriplani, Roya Rozati
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1Obstetrics2

Pregnancy with Previous Caesarean Section1

Deepti Goswami,
Alka Kriplani
 
INTRODUCTION
The rate of caesarean sections has progressively increased in both developed and the developing countries so obstetricians are faced with an increasingly large number of women who are pregnant following a delivery by caesarean section. Pregnancy in a woman with previous caesarean section is associated with an increased foetal mortality and morbidity along with an increased maternal morbidity and at times mortality. Trials of labour and elective repeat caesarean section have different risks and benefit. The evidence about the maternal and foetal safety with vaginal delivery or repeat caesarean is conflicting and contributes to uncertainties in management of these cases. Many aspects of trial of labour thus remain controversial at the dawn of 21st century.
The catchy aphorism ‘once a caesarean always a caesarean’ came from a paper published in 1916, entitled ‘Conservatism in Obstetrics’. It was not a recommendation, but rather an observation and a caution to avoid primary caesarean if at all possible as it may doom the woman to surgical deliveries in the future pregnancies. Trial of labour after caesarean section is an important strategy for lowering the rate of caesarean delivery.1 There are few absolute contraindications. The success rate of vaginal birth after previous caesarean is reported to be 60 to 80 per cent. Overall attempted vaginal birth for women with a single previous low transverse caesarean section is associated with a lower risk of complications than caesarean section. However, obstetrician's fear of uterine rupture is justified particularly in developing countries like India where take up of antenatal care is poor and access to clinical facilities often difficult. Uterine rupture is a catastrophic complication with a high rate of maternal morbidity including hysterectomy, major haemorrhage, operative complications and wound problems. In rural obstetric practices it remains a significant cause of maternal mortality. Hence, the dictum ‘once a caesarean, always a hospital delivery’ should be followed in all the women with previous caesarean delivery.4
 
Safety Issues: Vaginal Versus Repeat Caesarean Delivery
Most forms of maternal morbidities are higher with caesarean section than with vaginal birth. There are risks of anaesthesia, operative injury, infection, postpartum pain, prolonged hospitalisation, increased cost and psychological morbidity. The maternal morbidity associated with successful vaginal birth is about one-fifths of elective caesarean. However, patients who experience failed vaginal birth after caesarean have higher risks of uterine disruption and infectious morbidity compared with those who have successful vaginal delivery or elective repeat caesarean delivery. Failed trials of labour and subsequent caesarean causes almost twice the morbidity of elective section, but the lower morbidity in the 80 per cent of women who successfully deliver vaginally means that overall women who go in for a planned vaginal birth after caesarean suffer only half the morbidity of women who undergo an elective repeat section.
Though caesarean section may contribute to foetal risk in form of respiratory distress due to either the caesarean birth itself or due to preterm birth as a result of miscalculation of dates, the risk of perinatal death associated with labour after previous caesarean is reported to be higher than with a repeat caesarean section. The evidence from a meta analysis of 52 controlled studies involving 47,682 women shows that trial of labour may result in small increase in the uterine rupture rate and in foetal and neonatal mortality rates with respect to elective repeat caesarean delivery. Maternal morbidity, including febrile morbidity and the need for transfusion or hysterectomy may be reduced with a trial of labour.2
 
Management of Pregnancy with Previous Caesarean Section
This is a high risk pregnancy due to inherent risk of scar rupture which may occur antepartum, intrapartum or postpartum. The risk of scar rupture is mainly in late pregnancy and during labour. The antenatal care does not differ significantly except that at the booking visit, details of the previous pregnancy requiring caesarean should be documented and the tentative plan for mode of delivery formulated. A pelvic assessment is often made at 37 completed weeks of gestation if the woman is planned for trial of labour, however, there is no evidence for or against this practice. An elective caesarean, if decided for, is undertaken at 39 completed weeks of gestation to minimise the foetal risk of respiratory complications after the delivery.
It is important to educate the woman about need for continued antenatal surveillance and to promptly report to the hospital if she develops labour pains, vaginal bleeding or leaking per vaginum. The 5importance of the need for hospital delivery should be explained to her as well as her husband and/or family members.
 
Decision About the Mode of Delivery
Vaginal delivery is currently the preferred method of delivery for pregnant women who have undergone one previous low transverse caesarean section in absence of any contraindications. However, caution needs to be exercised in light of recent clinical data on the risks associated with this practice and proper selection of cases is vital for successful outcome. Although there has been effort to develop scoring system to predict the likelihood of success or failure for trial of labour after previous caesarean,3 these do not accurately predict the outcome in majority of the patients.
Indication for previous caesarean is an important determining factor for predicting success with attempted vaginal delivery. It is important to obtain as much information as possible about the circumstances of previous caesarean and previous notes should be examined if possible. Majority of indications are non recurrent; the group that needs to be identified is the one with possible recurrent indications for intrapartum caesarean section as they carry maximum risk of maternal complications as compared to vaginal delivery and elective repeat caesarean.4
A non-recurrent indication of previous caesarean section such as breech presentation or foetal distress is associated with a higher successful rate of vaginal delivery. Vaginal births are lowest when the initial indication was failure to progress in labour, dystocia or cephalopelvic disproportion. However, even with these latter indications, vaginal delivery was achieved in more than 50 per cent of the women in most published series, and the rate was over 75 per cent in the largest series reported.5 Thus, a history of caesarean section for dystocia is not a contraindication to subsequent vaginal delivery.
Previous vaginal span may be somewhat protective. In one study prior history of vaginal delivery was found to be the best predictor of positive outcome of trial of labour;6 this can be explained as in such cases pelvis gets proven to be clinically adequate. The advantage is increased further in those mothers whose previous vaginal birth occurred after, rather than before, the original caesarean section.
A short interdelivery interval or a history of postpartum fever during a previous caesarean may increase the risk of scar rupture during a trial of labour.7 Women delivering within 18 to 24 months of caesarean section should be counselled about the increased risk of uterine rupture in labour. A caution is needed in managing these cases particularly if other 6interventions that increase the risk of uterine rupture such as induction or augmentation become necessary.
The type of previous uterine incision should be documented as it has significant bearing on the risk of uterine rupture in attempted vaginal delivery. The overall risk of uterine rupture for lower segment transverse incisions in a review of 20,095 women giving birth after a previous caesarean has been shown to be 4.5 per 1000. The rate was 1.6 per 1000 in women having elective section and 5.2 per 1000 for women undergoing spontaneous labour.8 The risk that rupture may occur, that it may occur prior to onset of labour, and that it may have serious sequel, are much greater with classical than the low transverse uterine scar. The estimated risk for previous classical or ‘T’ incision is 4 to 9 per cent and for low vertical (De Lee) incision it is 1 to 7 per cent. Further the classical midline scar leads to the rapid ‘explosive’ rupture unlike the dehiscence after lower segment transverse incisions which are often silent, incomplete or incidentally discovered at the time of repeat caesarean section. Therefore, classical uterine scar and T shaped scar are in most cases a contraindication to the trial of labour. In situations where previous uterine incision is unknown but suggestive of classical one, elective repeat caesarean at term is advisable. When history of previous scar is unknown and unlikely to be classical, a trial of labour can be attempted after counselling. Close intrapartum surveillance is warranted in these cases.9
Since the 1990's single layer closure of uterus during caesarean is frequently practised. There is some concern regarding the increased risk of scar rupture during trial of labour in these women. However, all the studies involve patients who had two layered uterine closure and so far there is no evidence to support or refute this fear.10
The decision to perform a repeat caesarean or to permit a planned vaginal birth after caesarean would also take into consideration whether the foetus is alive, dead, anomalous or immature. The patient's wish for future pregnancies is also important when deciding for mode of delivery since a balance of risks will differ accordingly.
Pelvimetry is overall a poor predictor of obstetric outcome except when there is gross pelvic contraction as seen in cases with osteomalacia. Computed tomography pelvimetry is of no proven value either.11 Use of ultrasound to examine the scar thickness and thinning has been studied to decide about the mode of delivery.12 It has poor reproducibility and has failed to show a critical value below which scar rupture is inevitable if vaginal delivery is permitted.
In the era of increasing litigation, documentation of the discussion made with the patient regarding issues relating to delivery and the final decision reached, is of vital importance.7
 
Intrapartum Management
The trial of vaginal delivery should be undertaken at a centre well equipped to handle emergency operative intervention if needed and senior consultant should be involved in the decision making. At the onset of labour an intravenous access is secured and blood is sent for grouping and save.
Use of oxytocics: The use of oxytocin or prostaglandins for induction or augmentation of labour in women with previous caesarean has remained controversial due to speculation that it might increase the risk of scar rupture or dehiscence. Amniotomy with oxytocin is preferable to prostaglandin induction as the risk of complications from this method of induction appear to be lower. Use of Foley's catheter has been found to be safe for ripening the cervix in these women in one of the studies.13
Use of oxytocin for induction or augmentation increases the risk of scar dehiscence to 8 per 1000; the risk with prostaglandins is reported to be as high as 24.5 per 1000.14 These agents should therefore be used with the caution. High infusion rates of oxytocin should be avoided and dose increment should be no more frequent than every 30 min. The use of misoprostol is contraindicated for labour induction in these women as a number of case reports have shown it to be associated with an increased incidence of scar rupture.15
Epidural analgesia: Use of regional (caudal or epidural) analgesia in labour for women with previous caesarean section has been questioned due to fear that it would mask the pain and tenderness, which are considered to be the early signs of scar rupture. However this is not proven and epidural can be used in the same manner as for woman with intact uterus.16
Monitoring foetal well being during labour: Continuous electronic foetal heart monitoring is desirable as it allows early detection of foetal heart rate abnormalities before occurrence of uterine dehiscence. Intrauterine pressure catheters have not been shown to be reliable in detecting scar rupture.17
Monitoring the progress of labour: The progress of labour should be charted carefully on a partogram. The rate of cervical dilatation is no different from that for unscarred uterus.18 Deviation from the expected rate of progress requires careful assessment for possible cause and likelihood of obstructed labour contraindicating the use of oxytocin.
Scar exploration: There is no role of routine manual exploration of uterus to search for scar rupture or dehiscence in absence of any suggestive 8symptoms.19 It is often inconclusive as the lower uterine segment is thin and soft. It is painful to the woman and increases the risk of puerperal infective morbidity. An overzealous attempt may do more harm than good. In the absence of bleeding or systemic signs, a rupture without symptoms discovered postpartum does not require any treatment. A more prudent approach is to maintain an increased vigilance in the hour following the delivery of placenta for any signs suggestive of uterine scar rupture.
Instrumental delivery: The rate of instrumental delivery appears to be similar or slightly higher than that observed in primigravid women. Routine use of prophylactic forceps in second stage of labour is not indicated and is associated with increased incidence of maternal perineal trauma.
Scar rupture: Complete scar rupture involves all layers of uterus including the serosa with or without extrusion of the foetus. In a study of 60 cases of rupture uterus reported from a tertiary care centre in Delhi previous uterine scar was responsible for rupture in as high as 63.3 per cent cases.20
The highest risk for scar rupture is in the late first and in the second stage of labour. When using electronic foetal heart rate monitoring most common presentation of scar rupture is foetal heart rate abnormalities. There is no one specific FHR or uterine activity pattern that indicates the onset of a uterine rupture.21
If uterine contractions in labour suddenly cease in a patient with previous caesarean scar it should raise suspicion of scar rupture. Vaginal bleeding, abdominal tenderness on palpation, changes in the uterine shape and receding of the presenting part on vaginal examination are all predictive of uterine rupture. Postpartum uterine rupture presents with abdominal pain and tenderness or postpartum haemorrhage (PPH). Persistent PPH despite use of oxytocin should also raise the suspicion in these patients. Occasionally haematuria may occur either before or after delivery due to uterine rupture involving the urinary bladder.
In suspected intrapartum uterine scar rupture, immediate delivery by laparotomy should be undertaken by experienced consultant. Cross- matched blood should be arranged and experienced paediatric support should be available. After opening the abdomen, delivery of the baby is undertaken first followed by an assessment of the site and extent of scar rupture. There may be involvement of the bladder which requires careful identification and repair. Repair of the scar is done wherever possible; however hysterectomy may be required to control haemorrhage or if there is inability to repair the uterus. The rate of hysterectomy if rupture occurs may be as high as 25 per cent.229
Placental complications: Repeat caesarean delivery is associated with increased maternal morbidity and mortality from the placental pathologic conditions like placenta previa or accretes. When placenta previa occurs in patients with no previous caesarean risk of placenta accrete is 1 to 5 per cent, however the risk may be as high as 30 per cent in patients with one previous caesarean and higher if there are more than one.23
If an anterior placenta previa is diagnosed in a woman with a scarred uterus, the possibility of morbidly adherent placenta should be considered. This risk should be explained to the woman and the need for caesarean hysterectomy should be discussed and included in the written consent obtained prior to operative intervention. An elective caesarean section by an experienced surgeon is warranted in all such cases.
Special situations: The optimal management of labour in women with breech presentation, multiple gestation or in whom induction of labour is necessary is uncertain; the evidence as to the risks and benefit of a trial of labour is limited and obstetric management should be individualised after counselling.
Twins: In twin pregnancies with first twin presenting as vertex, a cautious trial of labour appears to be an effective and safe alternative to elective repeat caesarean section.24 However, further research is needed as the published studies do not have sufficiently large number of patients.
Breech presentation: In the western countries, particularly following the term breech study, there are recommendations for elective caesarean for breech presentation in the women with previous caesarean delivery, but the same practice cannot be universally advocated in a developing country like India where other socioeconomic factors need to be taken into consideration. External cephalic version for breech presentation is not contraindicated in women with previous caesarean section.25
Cost effectiveness: Cost effectiveness of trial of labour versus elective caesarean depends on likelihood of success at vaginal delivery. Although trial of labour is more expensive if it results in emergency caesarean section, high rate of successful vaginal delivery means that overall, trial of labour is about 30 per cent less expensive than elective caesarean.26,27
More than one previous caesarean: In a study from Saudi Arabia 103 of 115 (89%) of women with previous two caesareans delivered vaginally after trial of labour; there was one case of scar rupture who required hysterectomy.28 Though this suggests that trial of labour may be an option in the women with two previous low transverse uterine scars, in clinical practice most patients undergo planned elective caesarean section at term.10
 
CONCLUSION
A large proportion of caesarean sections are repeat caesarean births in most of the countries. The answer to rising caesarean rates seems to lie in reducing the primary caesarean section rates and judicious use of trial of vaginal delivery in women with previous caesarean birth. Vaginal birth after previous caesarean is both safe and effective under proper circumstances. Steps to achieve successful outcome with trial of labour would include careful selection of cases and developing guidelines for management of labour. Future research is needed to develop reliable methods of identifying women who will successfully deliver after trial of labour.
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