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Uterine rupture
Best Practice & Research Clinical Obstetrics and Gynaecology Vol. 16, No. 1, pp. 69±79, 2002
doi:10.1053/beog.2002.0256, available online at http://www.idealibrary.com on
6 Uterine rupture Michael J. Turner
MAO, FRCOG, FRCPI
Consultant Obstetrician and Gynaecologist, Coombe Women's Hospital, Dublin 8, Ireland
Uterine rupture is an uncommon obstetric event. It is important because it continues to be associated with maternal mortality, especially in developing countries, and with major maternal morbidity, particularly peripartum hysterectomy. It is also associated with a high incidence of perinatal mortality and morbidity worldwide. This chapter examines the incidence, aetiology, clinical presentation, complications and prevention of uterine rupture. The key factor in the cause of rupture is whether or not the uterus is scarred. Rupture of an unscarred uterus is rare, usually traumatic, and its incidence decreases with improvement in obstetric practice. Rupture of the scarred uterus is more common, and usually occurs after a trial of labour in a patient with a previous Caesarean section. This chapter also explores how the incidence and complications of uterine rupture may be minimized, and yet the incidence of vaginal birth after Caesarean section (VBAC) optimized, in clinical practice. Key words: uterine rupture; maternal mortality and morbidity; perinatal mortality and morbidity; vaginal birth after Caesarean section (VBAC).
Uterine rupture is an obstetric catastrophe. Despite the advances of modern medicine it continues to cause maternal and fetal mortality and morbidity. The pattern of uterine rupture has changed, especially in the developed world, with a decrease in ruptures associated with obstetric manipulative procedures and an increase in ruptures associated with a history of previous Caesarean section.1±4 The increase in the incidence of Caesarean delivery worldwide means that the decline in uterine rupture rates expected with improved obstetric care has not occurred. CLASSIFICATION There are two types of uterine rupture. Complete rupture involves the full thickness of the uterine wall. Incomplete rupture occurs when the visceral peritoneum remains intact. It is important to make this distinction because there are dierences between the two in terms of clinical presentation and rates of complication. Complete rupture presents usually as a dramatic emergency, which is potentially life-threatening for both mother and baby. Incomplete rupture presents typically as an asymptomatic dehiscence of a previous uterine scar found, but not always reported, at the time of Caesarean section. It is usually uncomplicated. It is also possible that asymptomatic scar dehiscence may occur following vaginal delivery, but remain undiagnosed. When it comes to measuring rates of uterine rupture, it is cases of complete rupture that are the most important clinically and that are likely to be reported accurately. 1521-6934/02/01006911 $35.00/00
c 2002 Elsevier Science Ltd. *
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INCIDENCE The incidence of uterine rupture varies locally and globally, and even within the same hospital evolves over time.2,5,6 The incidence of uterine rupture, for example, varies from one in 585 deliveries7 to one in 6673 deliveries.8 Indeed, the variation is so wide, and individual cases so infrequent, that all obstetric services should ideally audit and publish their own rates and distinguish between complete and incomplete rupture. In developed health services, uterine rupture now rarely results in maternal death but frequently results in signi®cant maternal morbidity, particularly peripartum hysterectomy and blood transfusion, and often results in fetal death.1,3,9 In contrast, 16.9% of total maternal deaths in an 8-year Nigerian review were due to uterine rupture, and the overall perinatal mortality was 86.3%.10 In a French review of maternal mortality in West Africa, uterine rupture accounted for 15% of obstetric deaths.11 AETIOLOGY In reviewing the recent literature, it is evident that the single most important factor in determining the risk of uterine rupture is whether the uterus has a previous scar or not. Rupture of an unscarred uterus is less frequent and usually traumatic in origin. It may result from obstetric manoeuvres such as internal version and breech extraction. Such manoeuvres were practised in the past in developed countries, and may continue to be practised in developing countries as obstetricians attempt to avoid Caesarean section, and thus, minimize maternal mortality and morbidity in circumstances where the anaesthetic services are often suboptimal. In developed countries, the improvements in medical care and, as a consequence, the increased use of Caesarean delivery, means that traumatic rupture of an unscarred uterus during pregnancy is now more likely to be associated with external trauma such as a road trac accident, domestic violence or gunshot wounds. Rupture of the unscarred uterus may rarely complicate, for example, an instrumental vaginal delivery (especially if it involves rotation of the fetal head), manual removal of the placenta, fetal surgery, shoulder dystocia, and surgical termination of pregnancy.12,13 In the developing world, rupture of the unscarred uterus may complicate obstructed labour, especially when a woman labours outside hospital. In the presence of medical care and in the absence of external or obstetric trauma, however, uterine rupture of an unscarred uterus is a rare event. Uterine rupture in a primigravida is so rare that it should raise the question as to whether the woman had a previous undisclosed pregnancy or uterine surgery. It is also so rare that the literature on uterine rupture in primigravida consists mainly of individual case reports. In our own hospital, for example, there was no case of rupture in 21 998 primigravidas delivered between 1982 and 1991, even though primigravidas are more likely to require oxytocin augmentation in labour.1 In contrast, a previous uterine scar is the major risk factor for uterine rupture, and the most common scar is that due to a previous Caesarean section. The uterus may also be scarred, for example, as a result of a previous perforation, a hysterotomy, a uteroplasty, cornual resection, a myomectomy (including laparoscopic) or previous fetal surgery. It is commonly believed that a uterine scar matters only if it is full thickness, for example, if the uterine cavity was opened at the time of myomectomy. There is little evidence, however, for this belief.
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The type of uterine scar, and in particular, the type of Caesarean section scar, matters. It matters because it determines the risk of rupture, the clinical presentation and the complication rate. A previous classical section, for example, is more likely to rupture and is associated with a higher incidence of an adverse maternal and fetal outcome compared with a previous lower segment Caesarean section. This may be explained by the fact that rupture of the lower segment usually occurs in the labour ward under supervision, whereas rupture of a previous classical scar may occur early in pregnancy either in the community or in the antenatal ward. Uterine rupture after classical Caesarean section has been reported as early as 15 weeks, gestation.14 The risk of uterine rupture after a classical Caesarean section is quoted as 4±9%, and after a previous lower segment Caesarean section as 0.2±1.5%.15 The incidence of rupture after a previous T-incision is regarded as being similar to that following a previous classical section.15 In the past there has been concern that patients with a prior lower vertical scar in the lower uterine segment may carry a similar risk of uterine rupture (UR) as women with a previous classical section. However, in a 12-year American study, the incidence of symptomatic UR in patients undergoing a trial of labour was 1% (n 28) in 2912 patients with a low transverse scar compared with 0.8% (n 3) in 377 patients with a low vertical scar. Women whose low vertical incision extended into the corpus of the uterus, however, were excluded from this study.16 The increase in population mobility in the modern world means that obstetricians often have to manage the pregnancy of a woman whose previous Caesarean section was performed in another hospital or, indeed, country. While such details should be sought, they may not be available prior to delivery. A random study of 200 patients set out to determine whether avoiding the augmentation of ineective contractions in women with unknown scars would decrease the risk of repeat Caesarean compared with awaiting the onset of a spontaneous labour.17 Oxytocin augmentation was associated with a higher rate of uterine scar separation (®ve versus zero), but there was no dierence in the incidence of repeat Caesarean section (16 versus 17%). Thus, where the details of the previous section are unknown, it is prudent to consider the possibility of a previous vertical scar in the upper uterine segment, especially in circumstances where the previous section was performed before 32 weeks' gestation or where there was a fetal anomaly. Such patients should be managed in labour as if they had a previous classical section scar. There are also studies that have examined the issue of the number of previous lower segment Caesarean sections. In a Chicago study, for example, of patients undergoing a trial of labour, the incidence of uterine separation was 2% (n 302) in women with more than one previous section compared with 1.1% (n 1110) in women with one previous section (NS).18 The authors concluded that a trial of labour could be permitted in patients with more than one previous section, provided that conditions permitted prompt recognition and treatment of emergencies.
CLINICAL PRESENTATION Uterine rupture may present antepartum, intrapartum or post-partum. Antepartum, abdominal pain is the most important clinical symptom. Vaginal bleeding may occur, but haemorrhage may be entirely intra-abdominal. There may be a history of abdominal trauma, but in the case of domestic violence it may be concealed. A history of uterine
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scarring is critical. Patients with a previous scar in the upper uterine segment may present early in pregnancy and may not experience uterine contractions before rupture. On examination, the woman may be clinically shocked. There may be abdominal tenderness, especially if the contents of the uterus have been released into the abdominal cavity. Tenderness over previous uterine scars is not a reliable sign of uterine rupture. The shape of the uterus may be distorted and the fetal parts easily palpable, but again, these signs are not reliable. Finally, there may be evidence of fetal distress or demise. The key feature, however, is the development of acute abdominal pain and signs of intra-abdominal haemorrhage in a woman with a history of previous uterine surgery or recent trauma. Scar dehiscence may present antepartum at the time of elective Caesarean section. Such cases are usually asymptomatic; there may be no signs pre-operatively and the dehiscence is easily repaired. Rupture of a previous lower segment Caesarean section scar antepartum is exceptional and it appears that, for whatever reason, rupture of the lower segment requires the onset of uterine contractions. As rupture of a previous classical section scar in contrast may occur antepartum, there is a strong case for the woman's supervision as an inpatient, certainly for the third trimester. Fortunately, delivery by classical section is now uncommon; for example, the incidence (including ®ve inverted-T incisions) was 0.073% (n 62), in 84 299 deliveries in Dublin.19 Intrapartum, the introduction of electronic fetal monitoring has meant that the most common presentation of uterine rupture is now fetal heart rate abnormalities.1,3 Although variable and or late decelerations occur before the onset of a fetal bradycardia, no one speci®c fetal heart rate or uterine activity pattern indicates the onset of rupture.20 In the presence of previous uterine scar, the development of fetal heart rate abnormalities should raise the suspicion of rupture. Such patients warrant review by a senior clinician, and the use of fetal blood sampling for a pH should not be allowed to delay the diagnosis and treatment. The use of catheters to monitor intrauterine pressure have not been shown to be helpful in the diagnosis of uterine rupture.21 Abdominal pain is also a common presentation of intrapartum uterine rupture,1 and the development of constant pain should raise a suspicion of either rupture or placental separation. There have been concerns that the widespread use of epidural analgesia in patients with a previous uterine scar may mask the pain of rupture, and thus, delay the diagnosis. The use of electronic fetal heart monitoring has meant, however, that fetal heart rate abnormalities usually precede the development of new symptoms. In labour, the symptom of abdominal tenderness due to rupture is more dicult to interpret in the presence of uterine contractions. The development of wound tenderness, changes in the uterine shape and palpation of fetal parts are suggestive of uterine rupture, but are unreliable. Vaginal bleeding may or may not occur. If uterine contractions in labour suddenly cease in a patient with a previous section scar, it should raise strong suspicions of uterine rupture. The administration of intravenous oxytocin to correct inecient uterine action in such a patient, therefore, may seriously compound a pre-existing problem. Post-partum, uterine rupture usually presents with abdominal pain and tenderness, and/or post-partum haemorrhage.1 Persistent post-partum haemorrhage despite the use of oxytocics should raise the possibility of rupture or, less commonly, uterine inversion. Occasionally, haematuria either before or during delivery may occur with uterine rupture when the rupture involves the bladder. Unexplained clinical shock may be due to rupture before, during or after delivery. The longer the delay in making the diagnosis and starting treatment, the greater the clinical risk.
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MANAGEMENT Once the diagnosis of complete uterine rupture is suspected, speed is of the essence. If the woman is clinically shocked, she needs to be resuscitated and this usually will include blood transfusion. At laparotomy, the diagnosis is con®rmed and the site and extent of the rupture quickly determined. If it has not already occurred, delivery of the baby is the ®rst priority. The body may already be partially or totally expelled from the uterus, and in such cases, the prognosis for the baby is grave and survival the exception. Once the baby and placenta are delivered, control of haemorrhage is a priority. The anatomy needs to be carefully identi®ed and this can be distorted, especially where the uterus ruptures into the bladder or broad ligament. Occasionally the uterus may rupture posteriorly, which makes the diagnosis more dicult. Also, curiously, sometimes the rupture may or may not be at the site of the previous uterine surgery. Once the problem has been fully evaluated, the obstetrician has to decide whether the rupture can be successfully repaired or whether hysterectomy is necessary. Repair is associated with lower morbidity, and has the important bene®t of preserving fertility. Tubal sterilization at the time of repair has been described, but such decisions are best not made in an emergency and should proceed only if already planned. Peripartum hysterectomy is associated with signi®cant morbidity and is best undertaken by an experienced surgeon. It may be technically easier, and thus safer, to perform a subtotal rather that a total hysterectomy. If the placenta is located in the lower segment, total hysterectomy may be necessary to prevent primary haemorrhage. PREVENTION As with all catastrophes, the subject of uterine rupture should not be discussed without considering prevention, and thus certain speci®c issues arise. Over the course of the last century, the incidence of uterine rupture in unscarred uteri decreased due to improved obstetric practices such as avoidance of internal version and obstructed labour. In the developing world initiatives have been undertaken, such as the use of partograms, to insure that women in obstructed labour receive medical care sooner rather than later. Such initiatives are important, but they have yet to be shown to prevent uterine rupture. Uterine rupture in now strongly associated with a history of previous Caesarean section, and rarely complicates spontaneous labour in either a primigravid or multigravid woman without a uterine scar. As with other spheres of human activity, there is pressure on obstetricians to take the short-term view when it comes to human reproduction. However, whenever a Caesarean section is performed, especially a classical Caesarean section, the obstetrician is increasing the risk for the individual woman of both uterine rupture and Caesarean hysterectomy in any future pregnancy.15,19 Regrettably, these serious long-term implications are often not considered in practice. The increasing incidence of primary Caesarean section means that it is inevitable that there is an increase in the number of women presenting for obstetric care with a history of a prior Caesarean section. It is axiomatic that avoiding the ®rst Caesarean section prevents uterine rupture in subsequent pregnancies. Indeed, it is this fear of rupture that is one of the main driving forces prompting many obstetricians to take the easy option and simply repeat the Caesarean delivery electively at term. While the
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maternal risks of repeat elective section are low in modernized health services, such an approach is not without risk for both mother and baby.22 As a result, most professional bodies encourage vaginal birth after Caesarean section (VBAC) in carefully selected cases.23,24 Such an approach can achieve high levels of vaginal delivery after a trial of labour with minimal risks to the mother.15 The use of oxytocics for induction of labour in patients with a previous uterine scar is controversial and the literature con¯icting. Some reviews have concluded that oxytocics, including prostaglandins, do not increase the risk of uterine rupture.25±28 The literature must, however, be interpreted with caution. Uterine rupture is an infrequent clinical event and it is dicult to obtain suciently large studies to show statistically that any individual practice is safe or dangerous. Prospective studies would have to include about 10 000 women in order to show a twofold increased relative risk.29 Also, many previous studies on the management of patients with a prior Caesarean section fail to draw the important distinction between oxytocics to induce labour and oxytocin to augment labour. Previous studies also include dierent combinations of oxytocic drugs and dierent routes of administration. In addition, results obtained in a carefully supervised research setting may not be applicable in worldwide clinical practice. Finally, in view of the medical and legal implications of uterine rupture, there may be publication bias because doctors may be understandably reluctant to publish serious complications. For all these reasons, the use of oxytocics, particularly prostaglandins, have not been proven to be safe practice for the widespread induction of labour with a previous uterine scar. There is evidence, indeed, that raises serious concerns. Retrospective reviews of clinical practice have found a strong association between induction of labour and uterine rupture.1,3 A recent multidisciplinary national review in the United Kingdom of 42 cases of uterine rupture associated with death of the baby found that labour was induced in 60% of the cases.30 In many of the inductions, the cervix was unfavourable and the presenting part high. More than half of the cases (n 25) received prostaglandins to induce labour. In a recent Canadian study of 2119 trials of labour among women with a previous Caesarean delivery, induction was associated with an increased risk of uterine rupture, and the association was highest when PGE2 gel was used.4 A large Swiss review of 29 046 deliveries after previous Caesarean section also found an association with induction of labour.31 In deciding whether or not to induce labour in a patient with a uterine scar, a critical factor is whether the patient has had a previous vaginal delivery or not. In a 2-year retrospective analysis in Dublin of induction of labour after one previous Caesarean section, the repeat section rate was 37.3% in 51 women who had never delivered vaginally compared with only 3.9% in the 52 women who had previously delivered vaginally (P 5 0.01).32 Fourteen women who had never delivered vaginally had an uneaced cervix at induction, and the repeat section rate in this group was 64.3%. There was one case of uterine rupture in each group, but, interestingly, both cases were in patients with an unfavourable cervix at the time of induction. These ®ndings are supported by an American study of 3783 women with one prior section allowed to labour which found a rupture rate of 1.1% among women without prior vaginal delivery, and 0.2% among women with prior vaginal delivery, (P 5 0.01).33 An Israeli study concluded that where a woman has achieved a vaginal birth after Caesarean section, the risk of rupture falls for subsequent deliveries.34 In a patient with a previous lower segment Caesarean section who has never had a vaginal delivery, if the cervix is unfavourable it is dicult to justify the risks of uterine rupture when the chances of a vaginal delivery are so low. In such circumstances it is preferable to await the spontaneous onset of labour ± or if there is a pressing need to
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deliver the baby an elective Caesarean section should be performed. If the patient with a previous lower segment Caesarean section has had a previous vaginal delivery and the cervix is favourable, induction of labour by amniotomy and intravenous oxytocin can safely achieve a high incidence of vaginal births. Apart from the use of oxytocin to induce labour, a meta-analysis of 31 studies reports that the use of oxytocin to augment labour is safe in a patient with a prior lower segment Caesarean section.35 Inecient uterine activity in a patient with a uterine scar may, however, be a sign that uterine rupture has already occurred and, therefore, it is recommended that the decision to use oxytocin is made by an experienced obstetrician only after a personal assessment including abdominal and vaginal examination.36 If labour does not progress despite oxytocin augmentation, the patient should be reviewed again earlier rather than later. This approach to augmentation of spontaneous labour with a previous uterine scar was associated with only three cases of rupture in 2832 patients allowed to labour.1 There continues to be considerable debate about the growing clinical dilemma of delivery after prior lower segment Caesarean section,15,37±39 and central to that debate is the risk of uterine rupture. If patients for trial of labour are carefully selected, if oxytocic agents are used cautiously, and if the patient is supervised closely, intrapartum and post-partum, obstetricians can achieve high rates of VBAC and yet minimize the risk of uterine rupture. Even if rupture occurs in such a carefully supervised setting, it should not carry the same risks to the mother and baby as rupture in other circumstances. UTERINE RUPTURE AFTER TWO OR MORE PREVIOUS CAESAREAN SECTIONS Information on the risks of uterine rupture following a trial of labour in patients with more than one previous lower segment Caesarean section is limited and, as family size decreases, it is going to be dicult to answer this question by clinical studies in the future. In a study of 115 women with two previous Caesareans who underwent a trial of labour, 89% delivered vaginally with one case of rupture (0.9%) necessitating hysterectomy.40 In a Moroccan study of 130 cases of trial of labour after two previous sections, 50% delivered vaginally and there were two cases of uterine rupture.41 In an American study of 134 patients with two previous sections allowed to trial of labour, the rate of uterine rupture was 3.7% compared with 0.8% following a trial of labour and one prior section.42 The high rate of rupture in this study, however, may be explained by the fact that in the patients with two previous Caesareans, 19.8% received oxytocics to induce labour and 38% received oxytocin to augment labour. If a patient with two or more previous Caesarean sections has had a previous vaginal delivery and is allowed to labour spontaneously, one could speculate that the chance of a vaginal birth is high and the chance of uterine rupture is minimal. It is dicult to prove such speculation as the number of women with three or more children suitable for such a study would be low. It might be answered, however, by a collaborative audit between hospitals with a large number of deliveries. DELIVERY AFTER PREVIOUS UTERINE RUPTURE As uterine rupture is a life-threatening experience and often results in hysterectomy, it is not surprising that there is little information on delivery after a previous uterine
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rupture. In a study of 18 pregnancies in 15 women who had repair of a uterine rupture, 17 babies were delivered by elective Caesarean section and one baby delivered vaginally at 28 weeks' gestation. There was no case of recurrent rupture.43 In a study from Qatar of 17 cases of uterine rupture, six patients subsequently became pregnant and delivered a total of 10 infants all by Caesarean section.44 While pregnancies after repair of a previous uterine rupture appears safe, it would be a brave obstetrician indeed who would allow a patient with a previous uterine rupture a trial of labour ASSESSMENT OF THE CAESAREAN SECTION SCAR Attempts have been made to assess the integrity of the lower uterine segment of patients with a prior Caesarean section using ultrasound antenatally. A prospective observational study of 642 patients in France found that the risk of uterine rupture and dehiscence was directly related to the degree of thinning of the lower segment at around 37 weeks of pregnancy. Using a thickness value of 3.5 mm or greater, the sensitivity was 88%, the speci®city was 73.2%, the positive predictive value was only 11.8%, and the negative predictive value was 99.3%.45 While the ®nding of a thick lower segment on ultrasound may reassure some obstetricians antenatally, there is no evidence that such measurements are superior to careful clinical practice in the prevention of rupture. In a Japanese study, serial transvaginal ultrasonography with full bladder was performed throughout pregnancy in 348 women with a previous Caesarean delivery. A lower uterine segment of less than 2 mm in thickness within 1 week of a repeat Caesarean section was associated with a 74% risk of scar dehiscence or rupture.46 Scar dehiscence, however, is usually uncomplicated. Based on the current evidence, it is likely that ultrasound measurements of the lower segment would increase the number of repeat elective Caesarean sections without any evidence that it is superior to clinical evaluation. In the past, it was common practice to perform a pelvic examination in a patient who had delivered vaginally following a previous Caesarean section to assess the integrity of the scar.47 Such a practice has now stopped because it is unreliable and may potentially precipitate the complication it was intended to diagnose. SUMMARY Recent advances in obstetric practice have resulted in a decrease in uterine ruptures due to trauma of an unscarred uterus and, at the same time, an increase in the number of ruptures following a trial of labour with a scarred uterus. While there have been improvements in maternal mortality following rupture, maternal morbidity and perinatal mortality remain high even when there is close medical supervision of pregnancy and labour. When it occurs antepartum, uterine rupture is usually traumatic, but may also complicate a previous classical section. When it occurs intrapartum and post-partum, rupture usually complicates a trial of labour following a previous Caesarean section and is associated with a lower incidence of complications than antepartum rupture. In patients with one prior lower segment Caesarean section, it is possible to minimize the risk of uterine rupture if the obstetrician selects carefully the patient suitable for a trial of labour and uses oxytocics with caution. As it is such an
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infrequent event, it is dicult to answer questions on the prevention, clinically, of uterine rupture. In particular, the literature on induction of labour following a previous Caesarean section is con¯icting. On balance, however, there is evidence that induction in a patient with an unfavourable cervix and a previous uterine scar places the woman at serious risk of uterine rupture. In the developing world, improvements in the health services are the key to avoiding uterine rupture of the unscarred uterus. Uterine rupture is such an important complication of pregnancy that all cases should be individually reviewed and subject to local audit.
Practice points . compared with incomplete rupture, complete uterine rupture usually presents as a dramatic emergency and the maternal and fetal complications are increased . rupture of an unscarred uterus in pregnancy is rare and is usually traumatic in origin. Antepartum the trauma is usually external, but peripartum it may result from obstetric intervention . uterine rupture in the absence of trauma in a primigravid woman is so rare it begs the question whether the woman had a previous undisclosed pregnancy or previous uterine surgery . in current practice, the major risk factor for uterine rupture is a previous Caesarean section . compared with a previous lower segment Caesarean section, a previous classical section scar is more likely to rupture, is more likely to result in serious complications, and the rupture may occur antepartum . in a patient with a previous lower segment Caesarean section who has never had a vaginal delivery, if the cervix is unfavourable it is dicult to justify the risk of uterine rupture by inducing labour when the chances of a vaginal delivery are low
Research agenda . uterine rupture is such an infrequent obstetric outcome that there are practical obstacles to performing randomized controlled trials . maternity services should individually review all cases of complete uterine rupture because it is such an important adverse obstetric outcome. Ideally, uterine rupture should be a subject of on-going local and regional audit . small studies suggesting that vaginal prostaglandins are safe for the induction of women with a previous Caesarean section need to be validated in clinical practice outside a research setting . in a woman with two previous lower segment Caesarean sections, further clinical research is required to determine whether, in carefully selected cases, she could safely be allowed a trial of labour, particularly in circumstances where she also has had a previous vaginal delivery . ultrasound evaluation of the uterine wall antepartum as a predictor of rupture or dehiscence warrants further studies
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REFERENCES *1. Gardeil F, Daly S & Turner MJ. Uterine rupture in pregnancy reviewed. European Journal of Obstetrics, Gynecology and Reproductive Biology 1994; 56: 107±110. 2. Chen LH, Tan KH & Yeo GS. A ten-year review of uterine rupture in modern obstetric practice. Annual Academy of Medicine Singapore 1995; 24: 830±835. *3. Baskett TF & Kieser KE. A 10-year population-based study of uterine rupture. Obstetrics and Gynecology 2001; 97: S69. *4. Ravasia DJ, Wood SL & Pollard JK. Uterine rupture during induced trial of labor among women with previous cesarean delivery. American Journal of Obstetrics and Gynecology 2000; 183: 1176±1179. 5. O'Driscoll K. Rupture of the uterus. Proceedings of the Royal Society of Medicine 1966; 59: 65±66. 6. Flannelly GM, Turner MJ, Rassmussen MJ & Stronge JM. Rupture of the uterus in Dublin; an update. Journal of Obstetrics and Gynaecology 1993; 13: 440±443. 7. Rahman J, Al Sibai MH & Rahman MS. Rupture of the uterus in labour: a review of 96 cases. Acta Obstetrica et Gynecologica Scandinavica 1985; 64: 311±315. 8. Spaulding LB & Gallup DG. Current concepts of management of rupture of the gravid uterus. Obstetrics and Gynecology 1979; 54: 437±441. *9. Appleton B, Targett C, Rasmussen M et al. Vaginal birth after Caesarean section: an Australian multicentre study. Australia and New Zealand Journal of Obstetrics and Gynaecology 2000; 40: 87±91. 10. Ola ER & Olamijulo JA. Rupture of the uterus at the Lagos University Teaching Hospital, Lagos, Nigeria. West Africa Journal of Medicine 1998; 17: 188±193. 11. Bouvier-Colle MH, Ouedraogo C, Dumont A et al. Material mortality in West Africa. Rates, causes and substandard care from a prospective survey. Acta Obstetrica et Gynecologica Scandinavica 2001; 80: 113. 12. Norman JE. Uterine rupture during therapeutic abortion in the second trimester using mifepristone and prostaglandin. British Journal of Obstetrics and Gynaecology 1995; 102: 332±333. 13. Miller DA, Goodwin TM, Gherman RB & Paul RH. Intrapartum rupture of the unscarred uterus. Obstetrics and Gynecology 1997; 89: 671±673. 14. Endres LK & Barnhart K. Spontaneous second trimester uterine rupture after classical cesarean. Obstetrics and Gynecology 2000; 95: 806±808. 15. Scott JR. Avoiding labor problems during vaginal birth after cesarean delivery. Clinical Obstetrics and Gynecology 1997; 40: 533±541. 16. Shipp TD, Zelop CM, Repke JT et al. Intrapartum uterine rupture and dehiscence in patients with prior lower uterine segment vertical and transverse incision. Obstetrics and Gynecology 1999; 94: 735±740. 17. Grubb DK, Kjos SL & Paul RH. Latent labor with an unknown uterine scar. Obstetrics and Gynecology 1996; 88: 351±355. 18. Asakura H & Myers SA. More than one previous cesarean delivery: a 5-year experience with 435 patients. Obstetrics and Gynecology 1995; 85: 924±929. 19. Greene RA, Fitzpatrick C & Turner MJ. What are the maternal implications of a classical Caesarean section? Journal of Obstetrics and Gynaecology 1998; 18: 345±347. 20. Menihan CA. Uterine rupture in women attempting a vaginal birth following prior cesarean birth. Journal of Perinatology 1998; 18: 440±443. 21. Beckley S, Gee H & Newton JR. Scar rupture in labour after previous lower uterine Caesarean section: the role of uterine activity measurements. British Journal of Obstetrics and Gynaecology 1991; 98: 265±269. 22. Jackson N & Paterson-Brown S. Physical sequelae of Caesarean section. BaillieÁre's Clinical Obstetrics and Gynaecology 2001; 15: 49±61. *23. Vaginal delivery after previous cesarean delivery. American College of Obstetricians and Gynecologists. Washington, DC, Practice Bulletin No. 5, 1999. 24. Society of Obstetricians and Gynaecologists of Canada. Clinical Practice Guidelines: vaginal birth after previous Caesarean section. Journal of the Society of Obstetricians and Gynaecologists of Canada 1997; 19: 1425±1428. 25. Chez RA. Cervical ripening and labor induction after previous cesarean delivery. Clinical Obstetrics and Gynecology 1995; 38: 287±292. 26. MacKenzie IZ, Bradley S & Embrey MP. Vaginal prostaglandins and labour induction for patients previously delivered by Caesarean section. British Journal of Obstetrics and Gynaecology 1984; 91: 7±10. 27. O'Connor KM. How safe is induction of labour following a previous Caesarean section? Journal of Obstetrics and Gynaecology 1983; 4: 86±87. 28. Stone JL, Lockwood CJ, Berkowitz G et al. Use of cervical prostaglandin E2 gel in patients with previous cesarean section. American Journal of Perinatology 1994; 11: 309±312. 29. Vause S & Macintosh M. Use of prostaglandins to induce labour in women with a Caesarean section scar. British Medical Journal 1999; 318: 1056±1058.
Uterine rupture 79 30. Focus Group ± ruptured uterus. A review of 42 cases of ruptured uterus associated with the death of the baby. CESDI, 5th Annual Report, 1998, pp 63±71. *31. Rageth JC, Juzi C & Grossenbacher H. Delivery after previous cesarean: a risk evaluation. Swiss Working Group of Obstetric and Gynecologic Institutions. Obstetrics and Gynecology 1999; 93: 332±337. *32. McNally OM & Turner MJ. Induction of labour after 1 previous Caesarean section. Australian and New Zealand Journal of Obstetrics and Gynaecology 2000; 39: 425±429. *33. Zelop CM, Shipp TD, Repke JT et al. Eect of previous vaginal delivery on the risk of uterine rupture during a subsequent trial of labour. American Journal of Obstetrics and Gynecology 2000; 183: 1184±1186. 34. Shimonovitz S, Botosneano A & Hochner-Celnikier D. Successful ®rst vaginal birth after Caesarean section: a predictor of reduced risk for uterine rupture in subsequent deliveries. Israel Medical Association Journal 2000; 2: 526±528. 35. Rosen MG, Dickinson JC & Westho CL. Vaginal birth after cesarean section: a meta-analysis of morbidity and mortality. Obstetrics and Gynecology 1991; 77: 465±470. 36. Turner MJ. Delivery after one previous cesarean section. American Journal of Obstetrics and Gynecology 1997; 176: 741±744. 37. McMahon MJ, Luther ER, Bowes WA & Olshan AF. Comparison of a trial of labor with an elective second cesarean section. New England Journal of Medicine 1996; 335: 689±695. 38. Flamm BL. Vaginal birth after Caesarean (VBAC). Clinical Obstetrics and Gynaecology 2001; 15: 81±109. 39. Mozurkewich EL & Hutton EK. Elective repeat cesarean delivery versus trial of labor: A meta-analysis of the literature from 1989 to 1999. American Journal of Obstetrics and Gynecology 2000; 183: 1187±1197. 40. Chattopadhyay SK, Sherbeeni MM & Anokute CC. Planned vaginal delivery after two previous Caesarean sections. British Journal of Obstetrics and Gynaecology 1994; 101: 498±500. 41. Abbassi H, el Karroumi M, Aboulfalah A et al. Trial of labor after 2 cesarean sections. Prospective study of 130 cases. Journal of Gynecology and Obstetric Biology Reproduction 1998; 27: 806±810. *42. Caughey AB, Shipp TD, Repke JT et al. Rate of uterine rupture during a trial of labor in women with one or two prior cesarean deliveries. American Journal of Obstetrics and Gynecology 1999; 181: 872±876. *43. O'Connor RA & Gaughan B. Pregnancy following simple repair of the ruptured gravid uterus. British Journal of Obstetrics and Gynaecology 1989; 96: 942±944. 44. Al Sakka M, Dauleh W & Al Hassani S. Case series of uterine rupture and subsequent pregnancy outcome. International Journal of Fertility and Women's Medicine 1999; 44: 297±300. 45. Rozenberg P, Gonet F, Philippe HJ & Nisand I. Ultrasonographic measurement of lower uterine segment to assess risk of defects of scarred uterus. Lancet 1996; 347: 281±284. 46. Gotoh H, Masuzaki H, Yoshida A et al. Predicting incomplete uterine rupture with vaginal sonography during the late second trimester in women with prior cesarean. Obstetrics and Gynecology 2000; 95: 596±600. 47. Perrotin F, Marret H, Fignon A et al. Scarred uterus: is routine exploration of the cesarean scar after vaginal birth always necessary? Journal of Gynecology and Obstetric Biology Reproduction 1999; 28: 253±262.
doi:10.1053/beog.2002.0256, available online at http://www.idealibrary.com on
6 Uterine rupture Michael J. Turner
MAO, FRCOG, FRCPI
Consultant Obstetrician and Gynaecologist, Coombe Women's Hospital, Dublin 8, Ireland
Uterine rupture is an uncommon obstetric event. It is important because it continues to be associated with maternal mortality, especially in developing countries, and with major maternal morbidity, particularly peripartum hysterectomy. It is also associated with a high incidence of perinatal mortality and morbidity worldwide. This chapter examines the incidence, aetiology, clinical presentation, complications and prevention of uterine rupture. The key factor in the cause of rupture is whether or not the uterus is scarred. Rupture of an unscarred uterus is rare, usually traumatic, and its incidence decreases with improvement in obstetric practice. Rupture of the scarred uterus is more common, and usually occurs after a trial of labour in a patient with a previous Caesarean section. This chapter also explores how the incidence and complications of uterine rupture may be minimized, and yet the incidence of vaginal birth after Caesarean section (VBAC) optimized, in clinical practice. Key words: uterine rupture; maternal mortality and morbidity; perinatal mortality and morbidity; vaginal birth after Caesarean section (VBAC).
Uterine rupture is an obstetric catastrophe. Despite the advances of modern medicine it continues to cause maternal and fetal mortality and morbidity. The pattern of uterine rupture has changed, especially in the developed world, with a decrease in ruptures associated with obstetric manipulative procedures and an increase in ruptures associated with a history of previous Caesarean section.1±4 The increase in the incidence of Caesarean delivery worldwide means that the decline in uterine rupture rates expected with improved obstetric care has not occurred. CLASSIFICATION There are two types of uterine rupture. Complete rupture involves the full thickness of the uterine wall. Incomplete rupture occurs when the visceral peritoneum remains intact. It is important to make this distinction because there are dierences between the two in terms of clinical presentation and rates of complication. Complete rupture presents usually as a dramatic emergency, which is potentially life-threatening for both mother and baby. Incomplete rupture presents typically as an asymptomatic dehiscence of a previous uterine scar found, but not always reported, at the time of Caesarean section. It is usually uncomplicated. It is also possible that asymptomatic scar dehiscence may occur following vaginal delivery, but remain undiagnosed. When it comes to measuring rates of uterine rupture, it is cases of complete rupture that are the most important clinically and that are likely to be reported accurately. 1521-6934/02/01006911 $35.00/00
c 2002 Elsevier Science Ltd. *
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INCIDENCE The incidence of uterine rupture varies locally and globally, and even within the same hospital evolves over time.2,5,6 The incidence of uterine rupture, for example, varies from one in 585 deliveries7 to one in 6673 deliveries.8 Indeed, the variation is so wide, and individual cases so infrequent, that all obstetric services should ideally audit and publish their own rates and distinguish between complete and incomplete rupture. In developed health services, uterine rupture now rarely results in maternal death but frequently results in signi®cant maternal morbidity, particularly peripartum hysterectomy and blood transfusion, and often results in fetal death.1,3,9 In contrast, 16.9% of total maternal deaths in an 8-year Nigerian review were due to uterine rupture, and the overall perinatal mortality was 86.3%.10 In a French review of maternal mortality in West Africa, uterine rupture accounted for 15% of obstetric deaths.11 AETIOLOGY In reviewing the recent literature, it is evident that the single most important factor in determining the risk of uterine rupture is whether the uterus has a previous scar or not. Rupture of an unscarred uterus is less frequent and usually traumatic in origin. It may result from obstetric manoeuvres such as internal version and breech extraction. Such manoeuvres were practised in the past in developed countries, and may continue to be practised in developing countries as obstetricians attempt to avoid Caesarean section, and thus, minimize maternal mortality and morbidity in circumstances where the anaesthetic services are often suboptimal. In developed countries, the improvements in medical care and, as a consequence, the increased use of Caesarean delivery, means that traumatic rupture of an unscarred uterus during pregnancy is now more likely to be associated with external trauma such as a road trac accident, domestic violence or gunshot wounds. Rupture of the unscarred uterus may rarely complicate, for example, an instrumental vaginal delivery (especially if it involves rotation of the fetal head), manual removal of the placenta, fetal surgery, shoulder dystocia, and surgical termination of pregnancy.12,13 In the developing world, rupture of the unscarred uterus may complicate obstructed labour, especially when a woman labours outside hospital. In the presence of medical care and in the absence of external or obstetric trauma, however, uterine rupture of an unscarred uterus is a rare event. Uterine rupture in a primigravida is so rare that it should raise the question as to whether the woman had a previous undisclosed pregnancy or uterine surgery. It is also so rare that the literature on uterine rupture in primigravida consists mainly of individual case reports. In our own hospital, for example, there was no case of rupture in 21 998 primigravidas delivered between 1982 and 1991, even though primigravidas are more likely to require oxytocin augmentation in labour.1 In contrast, a previous uterine scar is the major risk factor for uterine rupture, and the most common scar is that due to a previous Caesarean section. The uterus may also be scarred, for example, as a result of a previous perforation, a hysterotomy, a uteroplasty, cornual resection, a myomectomy (including laparoscopic) or previous fetal surgery. It is commonly believed that a uterine scar matters only if it is full thickness, for example, if the uterine cavity was opened at the time of myomectomy. There is little evidence, however, for this belief.
Uterine rupture 71
The type of uterine scar, and in particular, the type of Caesarean section scar, matters. It matters because it determines the risk of rupture, the clinical presentation and the complication rate. A previous classical section, for example, is more likely to rupture and is associated with a higher incidence of an adverse maternal and fetal outcome compared with a previous lower segment Caesarean section. This may be explained by the fact that rupture of the lower segment usually occurs in the labour ward under supervision, whereas rupture of a previous classical scar may occur early in pregnancy either in the community or in the antenatal ward. Uterine rupture after classical Caesarean section has been reported as early as 15 weeks, gestation.14 The risk of uterine rupture after a classical Caesarean section is quoted as 4±9%, and after a previous lower segment Caesarean section as 0.2±1.5%.15 The incidence of rupture after a previous T-incision is regarded as being similar to that following a previous classical section.15 In the past there has been concern that patients with a prior lower vertical scar in the lower uterine segment may carry a similar risk of uterine rupture (UR) as women with a previous classical section. However, in a 12-year American study, the incidence of symptomatic UR in patients undergoing a trial of labour was 1% (n 28) in 2912 patients with a low transverse scar compared with 0.8% (n 3) in 377 patients with a low vertical scar. Women whose low vertical incision extended into the corpus of the uterus, however, were excluded from this study.16 The increase in population mobility in the modern world means that obstetricians often have to manage the pregnancy of a woman whose previous Caesarean section was performed in another hospital or, indeed, country. While such details should be sought, they may not be available prior to delivery. A random study of 200 patients set out to determine whether avoiding the augmentation of ineective contractions in women with unknown scars would decrease the risk of repeat Caesarean compared with awaiting the onset of a spontaneous labour.17 Oxytocin augmentation was associated with a higher rate of uterine scar separation (®ve versus zero), but there was no dierence in the incidence of repeat Caesarean section (16 versus 17%). Thus, where the details of the previous section are unknown, it is prudent to consider the possibility of a previous vertical scar in the upper uterine segment, especially in circumstances where the previous section was performed before 32 weeks' gestation or where there was a fetal anomaly. Such patients should be managed in labour as if they had a previous classical section scar. There are also studies that have examined the issue of the number of previous lower segment Caesarean sections. In a Chicago study, for example, of patients undergoing a trial of labour, the incidence of uterine separation was 2% (n 302) in women with more than one previous section compared with 1.1% (n 1110) in women with one previous section (NS).18 The authors concluded that a trial of labour could be permitted in patients with more than one previous section, provided that conditions permitted prompt recognition and treatment of emergencies.
CLINICAL PRESENTATION Uterine rupture may present antepartum, intrapartum or post-partum. Antepartum, abdominal pain is the most important clinical symptom. Vaginal bleeding may occur, but haemorrhage may be entirely intra-abdominal. There may be a history of abdominal trauma, but in the case of domestic violence it may be concealed. A history of uterine
72 M. J. Turner
scarring is critical. Patients with a previous scar in the upper uterine segment may present early in pregnancy and may not experience uterine contractions before rupture. On examination, the woman may be clinically shocked. There may be abdominal tenderness, especially if the contents of the uterus have been released into the abdominal cavity. Tenderness over previous uterine scars is not a reliable sign of uterine rupture. The shape of the uterus may be distorted and the fetal parts easily palpable, but again, these signs are not reliable. Finally, there may be evidence of fetal distress or demise. The key feature, however, is the development of acute abdominal pain and signs of intra-abdominal haemorrhage in a woman with a history of previous uterine surgery or recent trauma. Scar dehiscence may present antepartum at the time of elective Caesarean section. Such cases are usually asymptomatic; there may be no signs pre-operatively and the dehiscence is easily repaired. Rupture of a previous lower segment Caesarean section scar antepartum is exceptional and it appears that, for whatever reason, rupture of the lower segment requires the onset of uterine contractions. As rupture of a previous classical section scar in contrast may occur antepartum, there is a strong case for the woman's supervision as an inpatient, certainly for the third trimester. Fortunately, delivery by classical section is now uncommon; for example, the incidence (including ®ve inverted-T incisions) was 0.073% (n 62), in 84 299 deliveries in Dublin.19 Intrapartum, the introduction of electronic fetal monitoring has meant that the most common presentation of uterine rupture is now fetal heart rate abnormalities.1,3 Although variable and or late decelerations occur before the onset of a fetal bradycardia, no one speci®c fetal heart rate or uterine activity pattern indicates the onset of rupture.20 In the presence of previous uterine scar, the development of fetal heart rate abnormalities should raise the suspicion of rupture. Such patients warrant review by a senior clinician, and the use of fetal blood sampling for a pH should not be allowed to delay the diagnosis and treatment. The use of catheters to monitor intrauterine pressure have not been shown to be helpful in the diagnosis of uterine rupture.21 Abdominal pain is also a common presentation of intrapartum uterine rupture,1 and the development of constant pain should raise a suspicion of either rupture or placental separation. There have been concerns that the widespread use of epidural analgesia in patients with a previous uterine scar may mask the pain of rupture, and thus, delay the diagnosis. The use of electronic fetal heart monitoring has meant, however, that fetal heart rate abnormalities usually precede the development of new symptoms. In labour, the symptom of abdominal tenderness due to rupture is more dicult to interpret in the presence of uterine contractions. The development of wound tenderness, changes in the uterine shape and palpation of fetal parts are suggestive of uterine rupture, but are unreliable. Vaginal bleeding may or may not occur. If uterine contractions in labour suddenly cease in a patient with a previous section scar, it should raise strong suspicions of uterine rupture. The administration of intravenous oxytocin to correct inecient uterine action in such a patient, therefore, may seriously compound a pre-existing problem. Post-partum, uterine rupture usually presents with abdominal pain and tenderness, and/or post-partum haemorrhage.1 Persistent post-partum haemorrhage despite the use of oxytocics should raise the possibility of rupture or, less commonly, uterine inversion. Occasionally, haematuria either before or during delivery may occur with uterine rupture when the rupture involves the bladder. Unexplained clinical shock may be due to rupture before, during or after delivery. The longer the delay in making the diagnosis and starting treatment, the greater the clinical risk.
Uterine rupture 73
MANAGEMENT Once the diagnosis of complete uterine rupture is suspected, speed is of the essence. If the woman is clinically shocked, she needs to be resuscitated and this usually will include blood transfusion. At laparotomy, the diagnosis is con®rmed and the site and extent of the rupture quickly determined. If it has not already occurred, delivery of the baby is the ®rst priority. The body may already be partially or totally expelled from the uterus, and in such cases, the prognosis for the baby is grave and survival the exception. Once the baby and placenta are delivered, control of haemorrhage is a priority. The anatomy needs to be carefully identi®ed and this can be distorted, especially where the uterus ruptures into the bladder or broad ligament. Occasionally the uterus may rupture posteriorly, which makes the diagnosis more dicult. Also, curiously, sometimes the rupture may or may not be at the site of the previous uterine surgery. Once the problem has been fully evaluated, the obstetrician has to decide whether the rupture can be successfully repaired or whether hysterectomy is necessary. Repair is associated with lower morbidity, and has the important bene®t of preserving fertility. Tubal sterilization at the time of repair has been described, but such decisions are best not made in an emergency and should proceed only if already planned. Peripartum hysterectomy is associated with signi®cant morbidity and is best undertaken by an experienced surgeon. It may be technically easier, and thus safer, to perform a subtotal rather that a total hysterectomy. If the placenta is located in the lower segment, total hysterectomy may be necessary to prevent primary haemorrhage. PREVENTION As with all catastrophes, the subject of uterine rupture should not be discussed without considering prevention, and thus certain speci®c issues arise. Over the course of the last century, the incidence of uterine rupture in unscarred uteri decreased due to improved obstetric practices such as avoidance of internal version and obstructed labour. In the developing world initiatives have been undertaken, such as the use of partograms, to insure that women in obstructed labour receive medical care sooner rather than later. Such initiatives are important, but they have yet to be shown to prevent uterine rupture. Uterine rupture in now strongly associated with a history of previous Caesarean section, and rarely complicates spontaneous labour in either a primigravid or multigravid woman without a uterine scar. As with other spheres of human activity, there is pressure on obstetricians to take the short-term view when it comes to human reproduction. However, whenever a Caesarean section is performed, especially a classical Caesarean section, the obstetrician is increasing the risk for the individual woman of both uterine rupture and Caesarean hysterectomy in any future pregnancy.15,19 Regrettably, these serious long-term implications are often not considered in practice. The increasing incidence of primary Caesarean section means that it is inevitable that there is an increase in the number of women presenting for obstetric care with a history of a prior Caesarean section. It is axiomatic that avoiding the ®rst Caesarean section prevents uterine rupture in subsequent pregnancies. Indeed, it is this fear of rupture that is one of the main driving forces prompting many obstetricians to take the easy option and simply repeat the Caesarean delivery electively at term. While the
74 M. J. Turner
maternal risks of repeat elective section are low in modernized health services, such an approach is not without risk for both mother and baby.22 As a result, most professional bodies encourage vaginal birth after Caesarean section (VBAC) in carefully selected cases.23,24 Such an approach can achieve high levels of vaginal delivery after a trial of labour with minimal risks to the mother.15 The use of oxytocics for induction of labour in patients with a previous uterine scar is controversial and the literature con¯icting. Some reviews have concluded that oxytocics, including prostaglandins, do not increase the risk of uterine rupture.25±28 The literature must, however, be interpreted with caution. Uterine rupture is an infrequent clinical event and it is dicult to obtain suciently large studies to show statistically that any individual practice is safe or dangerous. Prospective studies would have to include about 10 000 women in order to show a twofold increased relative risk.29 Also, many previous studies on the management of patients with a prior Caesarean section fail to draw the important distinction between oxytocics to induce labour and oxytocin to augment labour. Previous studies also include dierent combinations of oxytocic drugs and dierent routes of administration. In addition, results obtained in a carefully supervised research setting may not be applicable in worldwide clinical practice. Finally, in view of the medical and legal implications of uterine rupture, there may be publication bias because doctors may be understandably reluctant to publish serious complications. For all these reasons, the use of oxytocics, particularly prostaglandins, have not been proven to be safe practice for the widespread induction of labour with a previous uterine scar. There is evidence, indeed, that raises serious concerns. Retrospective reviews of clinical practice have found a strong association between induction of labour and uterine rupture.1,3 A recent multidisciplinary national review in the United Kingdom of 42 cases of uterine rupture associated with death of the baby found that labour was induced in 60% of the cases.30 In many of the inductions, the cervix was unfavourable and the presenting part high. More than half of the cases (n 25) received prostaglandins to induce labour. In a recent Canadian study of 2119 trials of labour among women with a previous Caesarean delivery, induction was associated with an increased risk of uterine rupture, and the association was highest when PGE2 gel was used.4 A large Swiss review of 29 046 deliveries after previous Caesarean section also found an association with induction of labour.31 In deciding whether or not to induce labour in a patient with a uterine scar, a critical factor is whether the patient has had a previous vaginal delivery or not. In a 2-year retrospective analysis in Dublin of induction of labour after one previous Caesarean section, the repeat section rate was 37.3% in 51 women who had never delivered vaginally compared with only 3.9% in the 52 women who had previously delivered vaginally (P 5 0.01).32 Fourteen women who had never delivered vaginally had an uneaced cervix at induction, and the repeat section rate in this group was 64.3%. There was one case of uterine rupture in each group, but, interestingly, both cases were in patients with an unfavourable cervix at the time of induction. These ®ndings are supported by an American study of 3783 women with one prior section allowed to labour which found a rupture rate of 1.1% among women without prior vaginal delivery, and 0.2% among women with prior vaginal delivery, (P 5 0.01).33 An Israeli study concluded that where a woman has achieved a vaginal birth after Caesarean section, the risk of rupture falls for subsequent deliveries.34 In a patient with a previous lower segment Caesarean section who has never had a vaginal delivery, if the cervix is unfavourable it is dicult to justify the risks of uterine rupture when the chances of a vaginal delivery are so low. In such circumstances it is preferable to await the spontaneous onset of labour ± or if there is a pressing need to
Uterine rupture 75
deliver the baby an elective Caesarean section should be performed. If the patient with a previous lower segment Caesarean section has had a previous vaginal delivery and the cervix is favourable, induction of labour by amniotomy and intravenous oxytocin can safely achieve a high incidence of vaginal births. Apart from the use of oxytocin to induce labour, a meta-analysis of 31 studies reports that the use of oxytocin to augment labour is safe in a patient with a prior lower segment Caesarean section.35 Inecient uterine activity in a patient with a uterine scar may, however, be a sign that uterine rupture has already occurred and, therefore, it is recommended that the decision to use oxytocin is made by an experienced obstetrician only after a personal assessment including abdominal and vaginal examination.36 If labour does not progress despite oxytocin augmentation, the patient should be reviewed again earlier rather than later. This approach to augmentation of spontaneous labour with a previous uterine scar was associated with only three cases of rupture in 2832 patients allowed to labour.1 There continues to be considerable debate about the growing clinical dilemma of delivery after prior lower segment Caesarean section,15,37±39 and central to that debate is the risk of uterine rupture. If patients for trial of labour are carefully selected, if oxytocic agents are used cautiously, and if the patient is supervised closely, intrapartum and post-partum, obstetricians can achieve high rates of VBAC and yet minimize the risk of uterine rupture. Even if rupture occurs in such a carefully supervised setting, it should not carry the same risks to the mother and baby as rupture in other circumstances. UTERINE RUPTURE AFTER TWO OR MORE PREVIOUS CAESAREAN SECTIONS Information on the risks of uterine rupture following a trial of labour in patients with more than one previous lower segment Caesarean section is limited and, as family size decreases, it is going to be dicult to answer this question by clinical studies in the future. In a study of 115 women with two previous Caesareans who underwent a trial of labour, 89% delivered vaginally with one case of rupture (0.9%) necessitating hysterectomy.40 In a Moroccan study of 130 cases of trial of labour after two previous sections, 50% delivered vaginally and there were two cases of uterine rupture.41 In an American study of 134 patients with two previous sections allowed to trial of labour, the rate of uterine rupture was 3.7% compared with 0.8% following a trial of labour and one prior section.42 The high rate of rupture in this study, however, may be explained by the fact that in the patients with two previous Caesareans, 19.8% received oxytocics to induce labour and 38% received oxytocin to augment labour. If a patient with two or more previous Caesarean sections has had a previous vaginal delivery and is allowed to labour spontaneously, one could speculate that the chance of a vaginal birth is high and the chance of uterine rupture is minimal. It is dicult to prove such speculation as the number of women with three or more children suitable for such a study would be low. It might be answered, however, by a collaborative audit between hospitals with a large number of deliveries. DELIVERY AFTER PREVIOUS UTERINE RUPTURE As uterine rupture is a life-threatening experience and often results in hysterectomy, it is not surprising that there is little information on delivery after a previous uterine
76 M. J. Turner
rupture. In a study of 18 pregnancies in 15 women who had repair of a uterine rupture, 17 babies were delivered by elective Caesarean section and one baby delivered vaginally at 28 weeks' gestation. There was no case of recurrent rupture.43 In a study from Qatar of 17 cases of uterine rupture, six patients subsequently became pregnant and delivered a total of 10 infants all by Caesarean section.44 While pregnancies after repair of a previous uterine rupture appears safe, it would be a brave obstetrician indeed who would allow a patient with a previous uterine rupture a trial of labour ASSESSMENT OF THE CAESAREAN SECTION SCAR Attempts have been made to assess the integrity of the lower uterine segment of patients with a prior Caesarean section using ultrasound antenatally. A prospective observational study of 642 patients in France found that the risk of uterine rupture and dehiscence was directly related to the degree of thinning of the lower segment at around 37 weeks of pregnancy. Using a thickness value of 3.5 mm or greater, the sensitivity was 88%, the speci®city was 73.2%, the positive predictive value was only 11.8%, and the negative predictive value was 99.3%.45 While the ®nding of a thick lower segment on ultrasound may reassure some obstetricians antenatally, there is no evidence that such measurements are superior to careful clinical practice in the prevention of rupture. In a Japanese study, serial transvaginal ultrasonography with full bladder was performed throughout pregnancy in 348 women with a previous Caesarean delivery. A lower uterine segment of less than 2 mm in thickness within 1 week of a repeat Caesarean section was associated with a 74% risk of scar dehiscence or rupture.46 Scar dehiscence, however, is usually uncomplicated. Based on the current evidence, it is likely that ultrasound measurements of the lower segment would increase the number of repeat elective Caesarean sections without any evidence that it is superior to clinical evaluation. In the past, it was common practice to perform a pelvic examination in a patient who had delivered vaginally following a previous Caesarean section to assess the integrity of the scar.47 Such a practice has now stopped because it is unreliable and may potentially precipitate the complication it was intended to diagnose. SUMMARY Recent advances in obstetric practice have resulted in a decrease in uterine ruptures due to trauma of an unscarred uterus and, at the same time, an increase in the number of ruptures following a trial of labour with a scarred uterus. While there have been improvements in maternal mortality following rupture, maternal morbidity and perinatal mortality remain high even when there is close medical supervision of pregnancy and labour. When it occurs antepartum, uterine rupture is usually traumatic, but may also complicate a previous classical section. When it occurs intrapartum and post-partum, rupture usually complicates a trial of labour following a previous Caesarean section and is associated with a lower incidence of complications than antepartum rupture. In patients with one prior lower segment Caesarean section, it is possible to minimize the risk of uterine rupture if the obstetrician selects carefully the patient suitable for a trial of labour and uses oxytocics with caution. As it is such an
Uterine rupture 77
infrequent event, it is dicult to answer questions on the prevention, clinically, of uterine rupture. In particular, the literature on induction of labour following a previous Caesarean section is con¯icting. On balance, however, there is evidence that induction in a patient with an unfavourable cervix and a previous uterine scar places the woman at serious risk of uterine rupture. In the developing world, improvements in the health services are the key to avoiding uterine rupture of the unscarred uterus. Uterine rupture is such an important complication of pregnancy that all cases should be individually reviewed and subject to local audit.
Practice points . compared with incomplete rupture, complete uterine rupture usually presents as a dramatic emergency and the maternal and fetal complications are increased . rupture of an unscarred uterus in pregnancy is rare and is usually traumatic in origin. Antepartum the trauma is usually external, but peripartum it may result from obstetric intervention . uterine rupture in the absence of trauma in a primigravid woman is so rare it begs the question whether the woman had a previous undisclosed pregnancy or previous uterine surgery . in current practice, the major risk factor for uterine rupture is a previous Caesarean section . compared with a previous lower segment Caesarean section, a previous classical section scar is more likely to rupture, is more likely to result in serious complications, and the rupture may occur antepartum . in a patient with a previous lower segment Caesarean section who has never had a vaginal delivery, if the cervix is unfavourable it is dicult to justify the risk of uterine rupture by inducing labour when the chances of a vaginal delivery are low
Research agenda . uterine rupture is such an infrequent obstetric outcome that there are practical obstacles to performing randomized controlled trials . maternity services should individually review all cases of complete uterine rupture because it is such an important adverse obstetric outcome. Ideally, uterine rupture should be a subject of on-going local and regional audit . small studies suggesting that vaginal prostaglandins are safe for the induction of women with a previous Caesarean section need to be validated in clinical practice outside a research setting . in a woman with two previous lower segment Caesarean sections, further clinical research is required to determine whether, in carefully selected cases, she could safely be allowed a trial of labour, particularly in circumstances where she also has had a previous vaginal delivery . ultrasound evaluation of the uterine wall antepartum as a predictor of rupture or dehiscence warrants further studies
78 M. J. Turner
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