OverviewUterine rupture in pregnancy is a rare and often catastrophic complication with a high incidence of fetal and maternal morbidity. Numerous factors are known to increase the risk of uterine rupture, but even in high-risk subgroups, the overall incidence of uterine rupture is low. From 1!"-#$1#, #% peer-reviewed publications described the incidence of uterine rupture, and these reported #,$&' cases among #,%1,#! pregnant women,yielding an overall uterine rupture rate of 1 in 1,1'" pregnancies ($.$!)*.+he initial signs and symptoms of uterine rupture are typically nonspecific, which makes the diagnosis difficult and sometimes delays definitive therapy. From the time of diagnosis to delivery, generally only 1$-,! minutes are available before clinically significant fetal morbidity becomes inevitable. Fetal morbidity occurs as a result ofcatastrophic hemorrhage, fetal ano-ia, or both.+he premonitory signs and symptoms of uterine rupture are inconsistent, and the short time for instituting definitive therapeutic action makes uterine rupture in pregnancy a much feared event for medical practitioners.DefinitionUterine rupture during pregnancy is a rare event and fre.uently results in life-threatening maternal and fetal compromise. /t can either occur in women with (1* a native, unscarred uterus or (#* a uterus with a surgical scarfrom previous surgery.Uterine rupture occurs when a full-thickness disruption of the uterine wall that also involves the overlying visceral peritoneum (uterine serosa* is present. 0y definition, it is associated with the following1 2linically significant uterine bleeding Fetal distress 3rotrusion or e-pulsion of the fetus and4or placenta into the abdominal cavity Need for prompt cesarean delivery Uterine repair or hysterectomy/n contrast to frank uterine rupture, uterine scar dehiscence involves the disruption and separation of a pree-isting uterine scar. Uterine scar dehiscence is a more common event than uterine rupture and seldom results in ma5or maternal or fetal complications./mportantly, when the defect in the uterine wall is limited to a scar dehiscence, it does not disrupt the overlying visceral peritoneum and it does not result in clinically significant bleeding from the edges of the pre-e-isting uterine scar. /n addition, in cases of uterine dehiscence (as opposed to uterine rupture*, the fetus, placenta, and umbilical cord remain contained within the uterine cavity. /f cesarean delivery is needed, it is for other obstetrical indications and not for fetal distress attributable to the uterine disruption.6lthough a uterine scar is a well-known risk factor for uterine rupture (most of which arise from prior cesarean delivery*, the ma5ority of events involving the disruption of uterine scars result in uterine scar dehiscence rather than uterine rupture. +hese two entities must be clearly distinguished, as the options for clinical management and the resulting clinical outcomes differ significantly.Sources of information and study selection+he peer-reviewed literature was searched using the 3ub7ed, 7edline, and 2ochrane databases for all relevant articles published in the 8nglish language. +he search terms were uterine rupture, pregnancy and priorcesarean section, vaginal birth after cesarean, 9062, trial of labor (+O:*, trial of labor after cesarean (+O:62*,uterine scar dehiscence, and pregnancy and myomectomy. ;tandard reference tracing was also used.6rticles published from 1!" through 7ay, #$1# that described the incidence of uterine rupture and that included sufficient information regarding the authors< definitions of uterine rupture and of uterine scar dehiscence were incorporated for review. 6ll studies were observational or reviews. 6 total of 1,, published articles were included for data e-traction and analysis.Incidence and risk factors7eta-analysis of pooled data from #% studies in the peer-reviewed medical literature published from 1!"-#$1#indicated an overall incidence of pregnancy-related uterine rupture of 1 per 1,'1" pregnancies ($.$!)*. =hen the studies were limited to a subset of & that provided data about the spontaneous rupture of unscarred uteri in developed countries, the rate was 1 per &,',' pregnancies ($.$1#)*.2ongenital uterine anomalies, multiparity, previous uterine myomectomy, the number and type of previous cesarean deliveries, fetal macrosomia, labor induction, uterine instrumentation, and uterine trauma all increase the risk of uterine rupture, whereas previous successful vaginal delivery and a prolonged interpregnancy interval after a previous cesarean delivery may confer relative protection. /n contrast to the availability of models to predict the success of a vaginal delivery after a +O:62, accurate models to predict the person-specific risk of uterine rupture in individual cases are not available.+he ma5or patient characteristics for determining the risk of uterine rupture are noted below.Uterine status is either native (unscarred* or scarred. ;carred status may include previous cesarean delivery, including the following1 ;ingle low transverse (further subcategori>ed by 1-layer or #-layer hysterectomy closure* ;ingle low vertical 2lassic vertical 7ultiple previous cesarean deliveries;carred status may also include previous myomectomy (transabdominal or laparoscopic*.Uterine configuration may be normal or may involve a congenital uterine anomaly.3regnancy considerations include the following1 ?rand multiparity 7aternal age 3lacentation (accreta, percreta, increta, previa, abruption* 2ornual (or angular* pregnancy Uterine overdistension (multiple gestation, polyhydramnios* @ystocia (fetal macrosomia, contracted pelvis* ?estation longer than '$ weeks +rophoblastic invasion of the myometrium ( hydatidiform mole, choriocarcinoma*3revious pregnancy and delivery history may include the following1 3revious successful vaginal delivery No previous vaginal delivery /nterdelivery interval:abor status is determined as follows1 Not in labor ;pontaneous labor /nduced labor - with o-ytocin, with prostaglandins 6ugmentation of labor with o-ytocin @uration of labor Obstructed laborObstetric management considerations include the following1 /nstrumentation ( forceps use* /ntrauterine manipulation (e-ternal cephalic version, internal podalic version, breech e-traction, shoulder dystocia, manual e-traction of placenta* Fundal pressureUterine trauma includes the following1 @irect uterine trauma (eg, motor vehicle accident, fall* 9iolence (eg, gunshot wound, blunt blow to abdomen*Aupture of the Unscarred Uterus+he normal, unscarred uterus is least susceptible to rupture. ?rand multiparity, neglected labor, malpresentation, breech e-traction, and uterine instrumentation are all predisposing factors for uterine rupture. 6 1$-year /rish study by ?ardeil et al showed that the overall rate of unscarred uterine rupture during pregnancy was 1 per ,$,!"' deliveries ($.$$,,)*. No cases of uterine rupture occurred among #1,& primigravidas, and only # ($.$$%1)* occurred among ,,%# multigravidas with no uterine scar.B1C6 meta-analysis of & large, modern (1!%-#$$* studies from industriali>ed countries revealed 1!' uterine ruptures among 1,'"!,%,' deliveries. +his finding suggests that the modern rate of unscarred uterine rupture during pregnancy is $.$1#) (1 in &,','*. +his rate of spontaneous uterine rupture has not changed appreciablyover the last %$ years, and most of these events occur at term and during labor. 6n &-fold increased incidence of uterine rupture of $.11) (1 in #$* has been noted in developing countries, with this increased incidence of uterine rupture having been attributed to a higher-than-average incidence of neglected and obstructed labor due to inade.uate access to medical care.=hen the risk of uterine rupture for women with different types of risk factors is assessed, these baseline rates of pregnancy-related uterine rupture in women with native, unscarred uteri, specifically, the rates of $.$1#) (1 in &,','* for women living in industriali>ed countries and $.11) (1 in #$* for women living in developing countries, represent observational benchmarks that should be referenced for all comparisons.8ffect of maternal parity7any authors have considered multiparity a risk factor for uterine rupture. ?olan et al noted that, in 1 of "1 cases (,1)*, uterine rupture occurred in women with a parity of more than %.B#C ;chrinsky and 0enson found that ! of ## women (,#)* who had unscarred uterine rupture had a parity of greater than '.B,C /n a study by 7okgokong and 7arivate, the mean parity for women who had pregnancy-related uterine rupture was '.B'C @espite the apparent increase in the risk of uterine rupture associated with high parity, ?ardeil et al found only# women with uterine rupture among ,,%# multigravidas who had no previous uterine scar ($.$$%)*.B1CAupture of the unscarred uterus before labor versus during labor;chrinsky and 0enson reported ## cases of uterine rupture in gravidas with unscarred uteri. Nineteen occurred during labor (&")*, and , occurred before labor (1')*. +his percentage was markedly different from that of gravidas with a previous uterine scar, for whom the timing of uterine rupture between labor and the antepartum period was nearly evenly distributed.B,CO-ytocin augmentation and induction of labor in the unscarred uterus+he use of o-ytocin for labor augmentation versus labor induction is often .uite different. +he two patient populations widely vary in their key attributes, as well as in the o-ytocin doses that are typically given, which systematically varies between the two groups. @espite this, many investigations concerning the use of o-ytocin and the risk of uterine rupture have failed to make this distinction./n 1!", 7okgokong and 7arivate reported #"$ uterine ruptures among 1,&$! deliveries that involved unscarred uteri, and ,# of the #"$ (1#)* were associated with o-ytocin use.B'C Aahman et al similarly found that o-ytocin was administered inof "% cases (1')* that involved unscarred uterine rupture.B%C ?olan et al noted that, among 1#",!1, deliveries, o-ytocin was used in #" of "1 cases (',)* that involved unscarred uterine rupture.B#C Dowever, 3lauche et al attributed only 1 of #, unscarred uterine ruptures (')* to the use of o-ytocin.B"C0ased on this type of limited information, the increased risk of uterine rupture attributable to the use of o-ytocin in gravidas with unscarred uteri is uncertain. Dowever, women who have had a cesarean delivery appear to have an increased risk of uterine rupture associated with the use of o-ytocin, both when it is used for labor augmentation and labor induction (see +able 1*.2ongenital uterine anomalies/n a review article, Nahum reported that congenital uterine anomalies affect appro-imately 1 in #$$ women.B!C /n such cases, the walls of the abnormal uteri tend to become abnormally thin as pregnancies advance, and the thickness can be inconsistent over different aspects of the myometrium (uterine musculature*.B&, , 1$, 11CAavasia et al reported an &) incidence of uterine rupture (# of #%* in women with congenitally malformed uteri compared with $."1) (11 of 1,!&&* in those with normal uteri (P E.$1,* who were attempting 9062.B1#C 0oth cases of uterine rupture in the women with uterine anomalies involved labor induction with prostaglandin 8#./n contrast, a study of 1"% patients with 7Fllerian duct anomalies who underwent spontaneous labor after 1 prior cesarean delivery reported no cases of uterine rupture.B1,C Of note, in this study ,") ("$ of 1"%* had only a minor uterine anomaly (arcuate or septate uterus*, and "') (1$% of 1"%* had a ma5or uterine anomaly (unicornuate, didelphys, or bicornuate uterus*. 7oreover, only ") (1$ of 1"%* of patients with 7Fllerian duct anomalies underwent induction of labor.For pregnancies that implant in a rudimentary horn of a uterus, a particularly high risk of uterine rupture is associated with the induction of labor (G &1)H ,&! of '!% cases*.B1'C /mportantly, &$) of ruptures involving these types of rudimentary horn pregnancies occurred before the third trimester, with "!) occurring during the second trimester.+he decision for induction of labor in women with a congenitally anomalous uterus, especially in cases of a previous cesarean delivery, must be carefully considered, given the higher incidence of uterine rupture reportedin this patient population. 6lthough the uterine rupture rate for unscarred anomalous uteri during pregnancy is increased relative to that for normal uteri, the precise increase in risk associated with the different types of uterine malformations remains uncertain.3revious Uterine 7yomectomy and Uterine Aupture3revious myomectomy by means of laparotomyNearly all uterine ruptures that involve uteri with myomectomy scars have occurred during the third trimester of pregnancy or during labor. Only 1 case of a spontaneous uterine rupture has been reported before #$ weeks ofgestation.B1%C0rown et al reported that among 1#$ term infants delivered after previous transabdominal myomectomy, no uterine ruptures occurred, and &$) of the infants were delivered vaginally.B1"C /n contrast, ?arnet identified , uterine ruptures among &, women (')* who had scars from a previous myomectomy and who underwent elective cesarean delivery because of previous myomectomy.B1!C;uch reports do not often delineate the factors that were deemed important for assessing the risk of subse.uent uterine rupture (eg, number, si>e, and locations of leiomyomataH number and locations of uterine incisionsH entry of the uterine cavityH type of closure techni.ue*. Further studies to investigate these issues are needed.3revious laparoscopic myomectomy@ubuisson et al reported 1$$ patients who underwent laparoscopic myomectomy and found , uterine ruptures during subse.uent pregnancies.B1&C Only 1 rupture occurred at the site of the previous myomectomy scar, resulting in the conclusion that the risk of pregnancy-related uterine rupture attributable to laparoscopic myomectomy is 1) (%) 2/, $-%.%)*. Dowever, the rarity of spontaneous uterine rupture raises the issue of whether the # uterine ruptures at sites that were not coincident with previous myomectomy scars were attributable to the previous myomectomies. /f so, a markedly higher ,) uterine rupture rate is associated with previous laparoscopic myomectomy.@ifferent authors reported no pregnancy-related uterine ruptures in ' studies of ,#$ pregnancies in women whopreviously underwent laparoscopic myomectomy.B1, #$, #1, ##C Dowever, in all ' studies, the number of patients who were allowed to labor was low, and a high percentage of deliveries were by scheduled cesarean delivery (&$), !), !%), and "%), respectively*./n a prospective study from Iapan, there were no uterine ruptures among % patients with a successful vaginal delivery after a prior laparoscopic myomectomy.B#,C /n a multicenter study in /taly with ,&" patients who achieved pregnancy after laparoscopic myomectomy, there was 1 recorded spontaneous uterine rupture at ,, weeks< gestation (rupture rate $.#")*.B#'CUterine rupture has been reported to occur as late as & years after laparoscopic myomectomy.B#%C +his findAupture of the ;carred Uterus @ue to 3revious 2esarean @elivery+he effect of previous cesarean delivery on the risk of uterine rupture has been studied e-tensively. /n a meta-analysis, 7o>urkewich and Dutton used pooled data from 11 studies and showed that the uterine rupture rate for women undergoing a +O:62 was $.,) compared with $.1") for patients undergoing elective repeat cesarean delivery (odds ratio BOAC, #.1$H %) 2/, 1.'%-,.$%*. 6fter restricting the meta-analysis to % prospective cohort trials, similar results were found (OA, #.$"H %) 2/, 1.'$-,.$'*.B#"CDibbard et al e-amined the risk of uterine rupture in 1,,#' women who underwent a +O:62. +hey reported a significant difference in the risk of uterine rupture between women who achieved successful vaginal birth compared with women in whom attempted vaginal delivery failed ($.##) vs 1.)H OA, &.H %) 2/, 1.-'#*.B#!C +he effect of previous cesarean delivery on the rate of subse.uent pregnancy-related uterine rupture can be further e-amined according to additional subcategories, which are summari>ed in +able 1.Aelevant to this issue of vaginal birth after cesarean section (9062* is that the overall rate in the United ;tates increased from ,.') in 1&$ to a peak of #&) in 1". 2ommensurate with this &-fold increase in the 9062 rate, reports of maternal and perinatal morbidity also increased, in particular with reference to uterine rupture. 0y #$$!, the 9062 rate in the United ;tates had fallen nationally to &.%). Not surprisingly, the cesarean delivery rate also reached an all-time high of ,#) in #$$!. /n its most recent guidelines pertaining to 9062 in 6ugust #$1$, the 6merican 2ongress of Obstetricians and ?ynecologists (62O?* adopted the recommendation not to restrict womenil*. Nevertheless, the vast ma5ority of cesarean deliveries performed in the United ;tates are accomplished via low-transverse uterine incisions./n a small case-control study of !$ patients by :eung et al, no association was found between an unknown uterine scar and the risk of uterine ruptureH however, given the rarity of uterine rupture (see +able 1*, this study was vastly underpowered to detect such a difference.B,!C +wo additional, but similarly underpowered, case serieshave also reported comparable rates of uterine rupture and 9062 success in women with unknown uterine cesarean delivery scars versus those with documented previous low-transverse hysterotomies.B,&, ,C +he 7aternal-Fetal 7edicine Units (7F7U* Network cesarean delivery registry reports a $.%) risk (1% of ,,#$"* of uterine rupture for patients who underwent a +O:62 with an unknown uterine scar.B,#CFor cases in which there are 1 or # unknown prior uterine incisions, there is a single small, randomi>ed, controlled trial by ?rubb et al that compared labor augmentation with o-ytocin (nE%* with no intervention (nE,* in women with prior cesarean deliveries involving either 1 or # unknown uterine incisions. Four uterine dehiscences and 1 uterine rupture occurred, all in the group that underwent labor augmentation. /n the 1 case of uterine rupture, the unknown uterine scar was in a patient with # prior cesarean deliveries, one of which involved a vertical incision. Dad the uterine scar status for this patient been known in advance, it would have represented a contraindication to +O:62.B'$CPrevious low transverse cesarean delivery+he risk of uterine rupture after a low transverse cesarean delivery varies depending on whether patients undergo a +O:62 or an elective repeat cesarean delivery and on whether labor is induced or spontaneous, as well as other factors. +he vast ma5ority of cesarean deliveries in the United ;tates are of the low transverse type. For women who have had 1 previous cesarean delivery, e-amining the various risk factors for uterine rupture is instructive. +hese absolute risks for uterine rupture are discussed below, as well as in +able 1.Previous cesarean delivery without a subsequent trial of labor/n a study of #$,$% women by :ydon-Aochelle et al, the spontaneous uterine rupture rate among ",&$ women with a single cesarean delivery scar who underwent scheduled repeat cesarean delivery without a +O: was $.1").B'1C +his finding indicates that uteri with cesarean scars have an intrinsic propensity for rupture that e-ceeds that of the unscarred organ during pregnancy, which is $.$1#) (OA increase of appro-imately 1#-fold*. +herefore, all other uterine rupture rates in women with a previous cesarean delivery should be referenced to this e-pected baseline rate.Previous cesarean delivery with subsequent spontaneous labor6 study by :ydon-Aochelle et al showed that the uterine rupture rate among 1$,!& women with a single previous cesarean delivery who labored spontaneously during a subse.uent singleton pregnancy was $.%#).B'1C +his rate of uterine rupture implies an increased relative risk (AA* of ,., (%) 2/, 1.&-".$* for women who labor spontaneously compared with women who undergo elective repeat cesarean delivery./n a study by Aavasia et al of 1,%'' patients with a previous cesarean delivery who later labored spontaneously, the uterine rupture rate was $.'%).B'#C Kelop et al found that, among #,#1' women with 1 previous cesarean delivery who labored spontaneously, the uterine rupture rate was $.!#).B',C +he authors of this article performed a meta-analysis of #,#", pregnancies fromstudies from 1&!-#$$' and showed that the overall risk of uterine rupture was $.'') for women who labor spontaneously after a previous cesarean delivery.Previous cesarean delivery with subsequent augmentation of labor@espite the clinical heterogeneity and different 9062 success rates for women undergoing spontaneous labor rather than either labor augmentation or induction, very few studies have stratified their data by labor augmentation versus labor induction and the data that do e-ist are conflicting. +here is wide variance in the fre.uency of clinical use of o-ytocin as well as in the dose and dosing schedules of o-ytocin that are used. 6s aresult, there is a paucity of specific evidence-based clinical guidelines for the use of o-ytocin in 9062 trials./n a study by 0lanchette et al, the rate of uterine rupture for #&& women who underwent o-ytocin augmentation of labor after a previous cesarean delivery was 1.'), compared with $.,') for ## women who underwent a trial of spontaneous labor. +his finding suggests a '-fold increased risk of uterine rupture in women who undergo labor augmentation with o-ytocin compared with spontaneous labor after a previous cesarean delivery./n the 7F7U Network study, the rate of uterine rupture with o-ytocin augmentation was $.) (%# of ",$$ cases* versus $.') (#' of ","&% cases* without o-ytocin use. /n contrast, a meta-analysis of studies published prior to 1& found that the use of o-ytocin was unassociated with uterine rupture.B#CKelop et al also found that labor augmentation with o-ytocin did not significantly increase the risk for uterine rupture.B'#C 3ooled data in +able 1 show a trend towards an increased rate of uterine rupture, albeit small, with o-ytocin use. Dowever, the conclusions to be drawn from this are both limited and suspect because, in general,no proper ad5ustment has been made for the potential (and very likely* confounding-by-indication that occurs in the observational studies that attempt to compare the rate of uterine rupture for women receiving treatment witho-ytocin versus those who do not (eg, proper propensity score matching has not been performed*./n this regard, assessment of the safety of o-ytocin use in 9062 trials must consider both the dosage and the time of e-posure. +hese issues were addressed by 2ahill et al in a nested case-control study of &$' patients within a multicenter, retrospective cohort of #%,$$% patients with at least 1 prior cesarean delivery who underwent a +O:62. 6t an intravenous o-ytocin dosage range of "-#$ mU4min, a more than ,-fold increased risk of uterine rupture was associated with o-ytocin use (DA Bha>ard ratioC, ,.,', %) 2/ 1.$1-1$.&*. 6t dosage range of more than #$ mU4min, a nearly '-fold increased risk of uterine rupture (DA, ,.#H %) 2/, 1.$"-1'.%#* was noted. +he attributable risk of uterine rupture associated with o-ytocin use was #.) and ,.")for the ma-imum o-ytocin dose ranges of more than #$ mU4min and more than ,$ mU4min, respectively.+he authors did not find a significant risk association between time (in terms of both duration of o-ytocin e-posure and duration of labor* and uterine rupture risk.+hey suggest an upper limit of #$ mU4min of o-ytocin for use in 9062 trials and a 5udicious approach to the use and monitoring of o-ytocin for both labor augmentation and induction.+he benefit of intrauterine pressure catheter (/U32* monitoring of uterine contractions in 9062 trials is unclear,with only a single small case series failing to detect differences in fetal or maternal morbidity4mortality associated with uterine rupture when an /U32 was used instead of e-ternal tocodynamometry. Nevertheless, many institutions have found the /U32 useful in allowing careful titration of o-ytocin dosing, especially when maternal habitus poses a limit to the accurate e-ternal monitoring of uterine contractions in women undergoing a +O:62.Previous cesarean delivery with subsequent induction of labor8merging data indicate that induction of labor after a prior cesarean delivery appears to be associated with an increased risk of uterine rupture.Kelop et al found that the rate of uterine rupture in %"$ women who underwent labor induction after a single previous cesarean delivery was #.,) compared with $.!#) for #,#1' women who had labored spontaneously (P E.$$1*.B',C/n a study by Aavasia et al of %!% patients who underwent labor induction, the uterine rupture rate was 1.') compared with $.'%) for women who labored spontaneously (P E.$$'*.B'#C0lanchette et al found that the uterine rupture rate after previous cesarean delivery when labor was induced was ') compared with $.,') for women who labored spontaneously.B''C +his last finding suggests a 1#-fold increased risk of uterine rupture for women who undergo labor induction after previous cesarean delivery.@ata on mechanical methods of labor induction for cervical ripening are limited but reassuring. /n a small case series, 0u5old et al found no statistically significant difference among the uterine rupture rates of 1.1) for spontaneous labor, 1.#) for induction by amniotomy with or without o-ytocin, and 1.") for induction by transcervical Foley catheter (P E$.&1*.B'%C2onversely, Doffman et al reported a ,."!-fold increased risk of uterine rupture (%) 2/, 1.'"-.#,* with Foley catheter use for preinduction cervical ripening. /mportantly, however, many of these patients received concomitant o-ytocin together with application of the transcervical Foley catheter.B'"COf particular note is that a recent randomi>ed controlled trial by 3ettker et al found that the addition of o-ytocin to the use of a transcervical Foley catheter for labor induction does not shorten the time to delivery and has no effect on either the likelihood of delivery within #' hours or the vaginal delivery rate.B'!C /n light of these findings, induction of labor with a transcervical Foley catheter alone may be a reasonable option for women undergoing a +O:62 with an unfavorable cervi-./n a more recent systematic review that evaluated maternal and neonatal outcomes following induction of labor (',$,& women* and spontaneous labor (1,,,!' women* in women who previously underwent cesarean section,Aossi and 3refumo reported a lower incidence of vaginal delivery with induced labor but higher rates of uterine rupture4dehiscence, repeat cesarean section, and postpartum hemorrhage.B'&CDysterectomy and neonatal outcomes were similar between the groups.Facchinetti et al indicated that women with a previous cesarean delivery being induced for premature rupture ofmembranes and who have a favorable 0ishop have a higher likelihood of success.B'C ;ignificant indicators for a vaginal delivery included a previous vaginal delivery, not being 6frican, and undergoing induction for premature rupture of membranes. =omen who underwent a repeat cesarean were more likely to have large babies (L ' kg* and had a higher likelihood of failing labor induction.B'CUse of prostaglandins for cervical ripening and induction of labor after previous cesarean delivery2urrent 62O? guidelines discourage the use of prostaglandins to induce labor in most women with a previous cesarean delivery. +his recommendation is based on considerable evidence for an increased risk of uterine rupture associated with prostaglandins. :ydon-Aochelle et al reported a 1%."-fold increased risk for uterine rupture (%) 2/, &.1-,$* when prostaglandins were used in gravidas who underwent a +O:62. /n ,"" women with scars from a previous cesarean delivery who underwent labor induction with prostaglandins, the uterine rupture rate was #.'%) compared with $.!!) without prostaglandin use.B'1C+aylor et al identified , uterine ruptures among %& patients with 1 previous cesarean delivery who received prostaglandin 8# (3?8#* alone for labor induction. +he uterine rupture rate was %.#) (, of %&* compared with 1.1) (& of !,#* among patients not treated with prostaglandin.B%$C Aavasia et al found that , ruptures occurred among 1!# patients who underwent labor induction with 3?8# alone (1.!)*, which was significantly higher than$.'%) (! of 1,%''* women who labored spontaneously.B'#C/n contrast, Flamm et al found a uterine rupture rate of 1.,) (" of '%,* in patients with a previous cesarean delivery who were treated with 3?8# in combination with o-ytocin. +his result was not significantly different from the rate of $.!) (,, of ',%"* in women who were not treated with 3?8#.B%1C /n a small study, @elaney and Moung also did not find a significant difference in uterine rupture rates between patients with scars from a previous cesarean delivery who underwent labor induction with 3?8# and patients with previous cesarean scars who labored spontaneously (1.1 vs $.,)H P E.1%*.B%#C:andon et al reported no uterine ruptures among ##! patients who underwent induction with prostaglandins alone. 6lthough the study was underpowered to detect small differences, the particular type of prostaglandin administered did not appear to significantly affect the uterine rupture rate (%# patients received misoprostolH 111, dinoprostoneH "$, 3?8# gelH and ', combined prostaglandins*.B,#CPrevious cesarean delivery with previous successful vaginal delivery;everal studies have shown a protective association of previous vaginal birth on uterine rupture risk in subse.uent attempts at vaginal birth after previous cesarean delivery. Kelop et al compared 1,$#1 women who underwent a +O: after a single previous cesarean delivery with 1 previous vaginal delivery with #,!"# women who underwent a +O: with no previous vaginal delivery. +he uterine rupture rate was $.#) versus 1.1) (P E.$1*.B%,C6mong women with a single uterine scar, those with at least 1 previous vaginal delivery had one fifth the risk foruterine rupture compared with women without a previous vaginal delivery (OA, $.#H %) 2/, $.$'-$.&*. 2aughey et al found that women with a previous vaginal delivery were about one fourth as likely as patients without a previous vaginal delivery to have a uterine rupture (OA, $.#"H %) 2/, $.$&-$.&&*.B%'C /n a study of #$% patients who underwent a +O: after 1 previous cesarean delivery, Nayani and 6lfirevic noted that all ' of their cases of uterine ruptures occurred in women with no previous vaginal delivery.B%%C6 study of 11,!!& women by members of the 7aternal-Fetal 7edicine Units (7F7U* Network found that in women with no prior vaginal delivery who underwent a +O:62, there was an increased risk of uterine rupture with induction versus spontaneous labor (1.%) vs $.&), P E$.$#*. /n contrast, no statistically significant difference was shown for women with a prior vaginal delivery who underwent spontaneous +O:62 compared with labor induction ($.") vs $.'), P E$.'#*.B%"CPrevious cesarean delivery with subsequent successful VB!s7ultiple studies suggest a protective advantage with regard to the uterine rupture rate if a woman has had a prior successful 9062 attempt. 7ultiple potential e-planations e-ist, but the # most obvious are that a successful prior 9062 attempt assures that (1* the maternal pelvis is tested and that the bony pelvis is ade.uate to permit passage of the fetus and (#* the integrity of the uterine scar has been tested previously under the stress4strain conditions during labor and delivery that were ade.uate to result in vaginal delivery without prior uterine rupture.7ercer et al found that the rate of uterine rupture decreased after the first successful 9062, but that there was no additional protective effect demonstrated thereafter1 the uterine rupture rate was $.&!) with no prior 9062s, $.'%) for those with one successful prior 9062, and $.',) for those with # or more successful prior 9062s (P E.$1*.B%!C 3ooled data from % studies indicate an increased uterine rupture rate of 1.') (1 per !,* in failed 9062 attempts that re.uired a repeat cesarean section in labor.B,#, '', %&, %, "$CInterdelivery interval/n a case-control study by 8sposito et al, an interpregnancy interval between cesarean delivery and a subse.uent pregnancy of O " months was nearly ' times as common among patients who had uterine rupture than in control sub5ects (1!.' vs '.!)H OA, ,.#H %) 2/, 1.$-1'.,*. 6mong #, patients who had uterine rupture after a previous cesarean delivery, the mean interpregnancy interval was #$.' P 1%.' months comparedwith ,".% P ,$.' months for control patients (P E.$1*.B"1C;tamilio et al recently confirmed a similar uterine rupturerate of #.!) in women with an interdelivery interval of O " months compared with $.) for those having interdelivery intervals of L" months (ad5usted OA #."", %) 2/, 1.#1-%.*.B"#C;hipp et al similarly found that the risk of symptomatic uterine rupture was increased ,-fold in women with interdelivery intervals ofO 1& months when they underwent a +O:62 after 1 previous cesarean delivery (OA, ,.$H %) 2/, 1.#-!.#*.B",C +he authors controlled for maternal age, public assistance, length of labor, gestational age of Q'1 weeks, and induction of augmentation of labor with o-ytocin./n additional support of this observation, a 2anadian study by 0u5old et al reported on 1,%#! women who underwent a +O: after a single previous low-transverse cesarean delivery, finding that #.&) of patients who had an interdelivery interval of G#' months had a uterine rupture compared with $.) for those with an interdelivery interval of R#' months (P O .$1*.B"'C 6fter ad5usting for confounding variables, the odds ratio for a uterine rupture during a subse.uent +O:62 was #."% for women who had an interdelivery interval of G#' months compared with women who had a longer interdelivery interval (%) 2/, 1.$&-%.'"*./n a follow-up study, the same authors e-amined the risk of uterine rupture between 1&-#' months. 6fter ad5ustment for confounding factors, they found that an interdelivery interval shorter than 1& months was associated with a significant increase of uterine rupture (odds ratio BOAC, ,H %) confidence interval B2/C, 1.,S!.#*, whereas an interdelivery interval of 1&-#' months was not (OA, 1.1H %) 2/, $.'S,.#*. /n agreement with the findings by ;hipp et al, the study by 0u5old et al concludes that an interdelivery interval shorter than 1& months but not between 1&-#' months should be considered as a risk factor for uterine rupture.B"%C+he authors speculated that a prolonged interpregnancy interval may allow time for the previous cesarean delivery scar to reach its ma-imal tensile strength before the scar undergoes the mechanical stress and strain with a subse.uent intrauterine pregnancy. /nterestingly, the authors also observed that the combination of a short interdelivery interval of G#' months and a single-layer hysterotomy closure was associated with a uterine rupture rate of %."). +his is comparable to the rate of uterine rupture for patients undergoing a +O:62 with a previous classic midline cesarean scar."ne#layer versus $#layer hysterotomy closure/n a 2anadian study of 1,&$ women who underwent a +O: after a single previous low transverse cesarean delivery, 0u5old et al found a '- to %-fold increased risk of uterine rupture for women who had a previous single-layer uterine closure compared with those having a two-layer closure. Uterine rupture occurred in ,.1) (1% of '& cases* of single-layer closure versus $.%) (& of 1,'1 cases* of two-layer closure (P O .$$1*. Using stepwise multivariate logistic regression, the authors concluded that the OA for uterine rupture in women who had undergone a single previous one-layer cesarean hysterotomy closure was ,.% (%) 2/, 1.,%-11.'* compared with those who had a two-layer closure.B""C+he same authors reported a multicenter, case-control study comparing " cases of uterine rupture with #&& controls. 3rior single-layer closure carried more than twice the risk of uterine rupture compared with two-layer closure. /n multivariate analysis, single-layer closure was linked to an increased rate of uterine rupture (odds ratio BOAC #."H %) confidence interval B2/C 1.,!S%.#&*. +he authors concluded that single-layer closure should be avoided in women who contemplate future 9062 delivery.B"!C@urnwald and 7ercer found that 1 patients with single-layer hysterotomy closure did not have an increased rate of uterine rupture, but the rate of uterine windows at subse.uent delivery was increased to ,.%) versus $.!) for those who had a multi-layer closure (P E.$'"*.B"&C?yamfi et al reported an &.") (, of ,%* rate of uterine rupture in patients with a single-layer closure compared with 1.,) (1# of 1,* in those with double-layer closure (P E$.$1%*. 6lthough the single-layer group had a shorter interdelivery interval, the uterine rupture rate remained significantly elevated even when the time interval was controlled for using logistic regression (OA !.#$, %) 2/, 1.&1-#&."#,P E$.$$%*.B"C%ultiple prior cesarean deliveriesFor women with a history of # or more cesarean deliveries, 1$ studies published from 1,-#$1$ showed that the risk of uterine rupture in a subse.uent pregnancy ranged from $.-".$) (1 per 1!-1$& pregnancies*. +his risk is increased #- to 1"-fold compared to women with only a single previous cesarean delivery. /n a study of 1!,,## women with scars from cesarean delivery, 7iller et al found that, when women underwent a +O:62, uterine rupture was , times more common with # or more scars (1.!)* than with 1 scar ($.")* BOA, ,.$"H %) 2/, 1.%-'.!H P O .$$1C.B!$C/n the largest analysis to date, 7acones et al reviewed data from 1! tertiary and community hospitals and found that, in 1,$ women with # uterine scars who underwent a +O:62, the risk of uterine rupture was increased #-fold compared with women with only 1 uterine scar (absolute rupture risk 1.&) vs $.)H ad5usted OA, #.,H %) 2/, 1.,!-,.&%*.B!1C/n the only study to control for potential confounding variables, 2aughey et al concluded that in women who had # previous cesarean deliveries who then attempted vaginal birth, the risk of uterine rupture was almost % times the risk of those with only 1 previous cesarean delivery (,.!) vs $.&)H P E.$$1*. +he study controlled for several key covariates, including the use of prostaglandin 8# gel, o-ytocin induction, o-ytocin augmentation, length of labor, and epidural use. +hey also found that women with a previous vaginal delivery were about one fourth as likely to have a uterine rupture as women without a previous vaginal delivery (OA, $.#"H %) 2/, $.$&-$.&&*.B%'C/n contrast, :andon et al reported through the 7F7U Network that there was no significant difference in the uterine rupture rate for women with multiple prior cesarean deliveries versus 1 prior cesarean delivery ($.) vs$.!)H P= $.,!*.B!#CDowever, in this study there was a much lower +O:62 rate of ) for women with multiple prior cesarean deliveries compared with the #!) rate in the report of 7acones et alB!1C and the !,) rate in 7illerJs study.B!$C +his indicates that there were much more stringent inclusion4e-clusion criteria applied by :andon et al, and that this difference may account for the apparent discrepancy in outcomes. 2aughey et al didnot report the +O:62 rate in their 1#-year data analysis.B%'C6 recent meta-analysis of 1! studies including %,""" patients undergoing a +O: after # or more cesarean deliveries demonstrated a 1.,") uterine rupture rate.B!,C+his is similar to the result of our pooled data analysis from 1$ studies published from 1,-#$1$, which shows a 1.&1) uterine rupture rate for patients with multiple previous cesarean delivery scars.6 #$$' 62O? guideline suggested that in women with # previous cesarean deliveries, only those with a previous vaginal delivery should be considered candidates for a +O:62.B!'C +his 62O? recommendation was subse.uently revised in an updated #$1$ guideline to suggest that women with two previous low transverse cesarean deliveries may be considered candidates for +O:62 regardless of their prior vaginal delivery status.B#&C%aternal age;hipp et al showed that advancing maternal age is associated with an increased rate of uterine rupture. /n a multiple logistic regression analysis designed to control for confounding factors, the overall rate of uterine rupture among ,,$1% women with 1 previous cesarean delivery was 1.1). +he rate of uterine rupture in womenolder than ,$ years (1.')* versus younger women ($.%)* differed significantly (OA, ,.#H %) 2/, 1.#-&.'*.B!%C%ultiple gestation7ost large series of 9062 with twin gestations report similar rates of uterine rupture for twin and singleton gestations. /n an analysis of the largest database of inpatient hospitali>ations available in the United ;tates from 1,-#$$#, Ford et al studied 1,&%$ women with twin gestations attempting 9062 and found similar uterine rupture rates compared with singleton gestations ($.) vs $.&)*.B!"C;imilarly, 2ahill et al compared %,% twin pregnancies with #',,$! singleton pregnancies and reported a comparable uterine rupture rate of 1.1) for twin vs $.) for singleton pregnancies (OA, 1.#H %) 2/, $.,-'."* in women with at least 1 previous cesarean delivery undergoing +O:62.B!!C 6dditionally, they found that patients with twins were less likely to attempt a +O:62 (OA, $.,H %) 2/ $.#-.$'*, but no more likely to have a 9062 failure (OA, 1.1H %) 2/, $.&-1."*, or ma5or maternal morbidity (OA, 1."H %) 2/, $.!-,.!*.Overall, women with multifetal gestations attempting 9062 did not incur any greater risk of uterine rupture thantheir singleton controls. /n a nested case-control study of the 7F7U cesarean registry, 9arner et al compared cases of women undergoing +O:62 with one previous cesarean delivery with a multifetal pregnancy versus controls with one previous cesarean delivery with a singleton pregnancy.B!&C6 similar uterine rupture rate of $.!)was found in both multifetal ('4%%"* versus singleton groups (41,,#,* BOAad5 1.1 ($.',-,.,$*C . /n a smaller study, 6aronson et al reported no cases of uterine rupture among 1,' twin pregnancies undergoing a +O:62 with a single prior cesarean section.B!C +he 62O? #$1$ guidelines for 9062 recommend that women with one previous cesarean delivery with a low transverse incision, who are otherwise appropriate candidates for twin vaginal delivery, may be considered candidates for +O:62.B#&C&etal macrosomia8lkousy et al found that, in ,"$ women who underwent a +O:62 after 1 previous cesarean delivery, the risk of uterine rupture was significantly greater for fetuses that weighed more than '$$$ g (#.&)* than in those weighing less than '$$$ g (1.#)H AA #.,, P O .$$1*. For women with 1 previous cesarean delivery and no previous vaginal deliveries, the uterine rupture rate was ,.") for women with a fetal weight of more than '$$$ g compared to women with a fetal weight of O '$$$ g (AA #.,, P O .$$1*.B&$C 7ore recently, Iastrow et al showed that birth weight was directly correlated with the rate of uterine rupture, with uterine rupture rates of $.), 1.&), and #.") for birth weights of less than ,%$$ g, ,%$$-, g, and '$$$ g or larger, respectively (P O .$%*.B&1CKelop et al reported that the rate of uterine rupture for women delivering neonates weighing R'$$$ g was 1.") versus 1) for newborns G'$$$ g, but that the difference was not statistically significant (P E$.#'*.BC Flamm et ale-amined +O:62 risks in a cohort of ,$1 women and reported no difference between the rates of uterine rupture for women with neonates weighing L'$$$ gm versus O '$$$ gm.B&,C +he 62O? #$1$ 9062 guidelines suggest that suspected fetal macrosomia alone should not preclude the possibility of +O:62.B#&C'estation beyond () weeks+he effect of advancing gestational age on the safety and success of +O:62 is of great clinical significance in the counseling of postterm 9062 candidates. /n a 2anadian study that evaluated ,# patients with advanced gestational age of L'1 weeks, Dammoud et al reported a significantly increased rate of uterine rupture of #.!) compared to 1.$) among 1,11 patients with gestational ages between ,!-'$ "4! weeks (pE$.$$"*.B&'C 6fter ad5usting for confounding variables, advanced gestational age was associated with a lower rate of successful vaginal delivery (OA $."&, %) 2/ $.%1S$.&* and a higher rate of uterine rupture (OA #.&%, %) 2/ 1.#!S".'#*when compared to those pregnancies of gestational age between ,!S'$ "4! weeks. ;imilarly, a 0ritish study byNiran et al found a significantly increased rate of uterine rupture of #.1) (1$ of '""* in women undergoing +O:62 beyond '$ weeks of gestation compared to $.,) (' of 1,1%'* forthosewithgestationalagesofG'$weeks(OA".,,2/1.-#$.#*.B&%C+he largest study to evaluate the effect of delivery beyond '$ weeks of gestation has not found this association, however. 6mong ',"&$ women undergoing a +O:62 at a gestational age of '$ weeks or longer, 2oassolo et al reported a uterine rupture rate of 1.1) (%# of ',"&$*, which was not statistically different from the uterine rupture rate of 1.$) ("& of ",$!* found in women with a gestational age of less than '$ weeks.B&"C =hen the investigational cohort was defined as those pregnancies of '1 weeks< gestation or longer, the risk of uterine rupture and overall morbidity was also not increased.+he difference in these results may arise from the small sample si>es of the 2anadian and 0ritish studies and4or the accuracy of gestational age estimates by last menstrual period dating with early ultrasound confirmation, which was not clearly defined in the study of 2oassalo et al. Kelop et al reported similar findings of no significant difference in uterine rupture rate of 1.,) (1! of 1,#!1* in women undergoing +O:62 at more than '$ weeks of gestation versus $.&) (1# of 1,%$'* in women at ,!-'$ weeks of gestation (3 E $.#*.B&!C7oreover, the latter authors reported that the risk of uterine rupture does not increase substantially after '$ weeks of gestation, but is increased with induction of labor regardless of gestational age. For spontaneous labor, uterine ruptures occurred in $.%) of gravidas delivering at or before '$ weeks compared with 1.$) for those delivering after '$ weeks (3 E $.#*. For induced labor, the rates of uterine rupture were #.1) for gravidasat or before '$ weeks and #.") for those after '$ weeks (3 E $.!*+he 62O? #$1$ 9062 guidelines suggest that although the chance of success may be lower for a vaginal delivery in more advanced gestations, gestational age beyond '$ weeks alone should not preclude a +O:62.B#&C BT+able1C+able 1. 6bsolute Aates of Uterine Aupture for @ifferent 3atient ;ubgroups (Open +able in a new window*General CategorySubcategory Uterine RuptureYearsof Data CollectionNo.of StudiesReferencesMajor MinorTotal DeliveriesRateTotal No.in Subcategory!ll NA NA 2,951,2971 per 1,426 (0.07%)2,084 1973-2010 25Gardeil 1994, Golan 1980, Scrin!"# 1978, $o"%o"on% 1976, &a'an 1985, (la)ce 1984, *andon 2004, Gre%or# 1999, $c$aon 1996, &a%e+ 1999, ,l"o)!# 2003, -ap 2001, *e)n% 1993, $iller 1997, .ie!er 2002, /)0old 2002, 12ir 2004, 3la'' 1994, $enian 1998, 45ar+ 2009Unscarred uterus6n ind)!+riali7ed co)n+rie!NA 1,467,5341 per 8,434 (0.013%)174 1975-2006 8Gardeil 1994, (la)ce 1984, Gre%or# 1999, &a%e+ 1999, -ap 2001, $iller 1997, .ie!er 2002, 45ar+, 20096n de8elopin% co)n+rie!NA 399,3141 per 920 (0.11%)434 1966-2006 4 Golan, 1980, $o"%o"on% 1976, &a'an 1985, G)p+a 2010,lec+i8e pri'ar# ce!arean deli8er#NA 17,2091 per 1,324 (0.08%)13 1995 1 Gre%or# 199991*A: NA 452,7201 per 4,975 (0.02%)91 1995 1 Gre%or# 1999*a;or 5i+ 8a%inal deli8er#NA 401,3871 per 14,866 (0.01%)27 1995 1 Gre%or# 19993ailed la;or 5i+ pri'ar# ce!arean deli8er#NA 51,3331 per 802 (0.12%)64 1995 1 Gre%or# 1999Congenitally ano"alous uterus(re8io)! lo5 +ran!8er!e ce!arean deli8er#NA 1901 per 95 (1.1%)2 1992-2002 2 &a8a!ia 1999, ,re7 2007Nor"al uterus# previous "yo"ecto"yNA NA 1,0011 per 143 (.70%)7 1930-2006 10/ro5n, 1956, Garne+ 1964, arner 2007, Aaron!on 2010 $)l+iple %e!+a+ion Ai+o)+ 91*A: (,&:arner 2005, 3ord 2006, Aaron!on 2010 3e+al 'acro!o'ia C4000 %2,2161 per 44 (2.3%)44 1984-2004 4 3la'' 1989 Ge!+a+ion ;e#ond 40 5ee"!6,7461 per 77 (1.3%)88 1984-2002 4 4elop 2001, =a''o)d 2004, :oa!!olo 2005, .iran 20066nd)ced la;or 5781 per 34 (2.9%)17 1984-2002 3 4elop 2001, =a''o)d 2004, :oa!!olo 2005,Spon+aneo)! la;or 1,4881 per 78 (1.3%)19 1984-2002 3 4elop 2001, =a''o)d 2004, :oa!!olo 2005,En"no5n )+erine !carNA 3,6981 per 218 (0.5%)17 1999-2002 4 *andon 2004, (r)e++ 1988, /eall 1984, Gr);; 1996*o5 8er+ical ce!arean deli8er#NA 1,3551 per90 (1.1%)15 1981-2002 6 *andon 2004, Nae2 1995, Adair 1996, $ar+in 1997, Sipp 1999, 4elop 1999Ai+ la;or 9331 per 104 (0.96%)9 1981-1997 3 Nae2 1995, $ar+in 1997, Sipp 1999Nor"al uterus# "ultiple previous cesarean deliveriesNA NA 6,2791 per54 (1.85%)116 1983-2002 10/lance++e 2001, 4elop 2000, :a)%e# 1999, $iller 1994, $acone! 2005, *andon 2006,*e)n% 1993, :o5an 1994, A!a")ra 1995, :aill 2010Spon+aneo)! 91* NA 5231 per 131 (0.76%)4 1996-2002 1 *in 20046nd)ced 91*(o@#+ocin)NA 541 per54 (1.8%)1 1996-2002 1 *in 20046nd)ced 91*(pro!+a-%landin)NA 191 per19 (5.3%)1 1996-2002 1 *in 2004NAFNo+ applica;le91*A:F9rial o2 la;or a2+er ce!arean>/A:F>a%inal ;ir+ a2+er ce!arean deli8er#;igns and ;ymptoms of Uterine Aupture @uring 3regnancy+he signs and symptoms of uterine rupture largely depend on the timing, site, and e-tent of the uterine defect. Uterine rupture at the site of a previous uterine scar is typically less violent and less dramatic than a spontaneous or traumatic rupture because of their relatively reduced vascularity.+he classic signs and symptoms of uterine rupture are (1* fetal distress (as evidenced most often by abnormalities in fetal heart rate*, (#* diminished baseline uterine pressure, (,* loss of uterine contractility, ('* abdominal pain, (%* recession of the presenting fetal part, ("* hemorrhage, and (!* shock. Dowever, modern studies show that some of these signs and symptoms are rare and that many may not be reliably distinguished from their occurrences in other, more benign obstetric circumstances (see +able #*.+able #. 2onditions 6ssociated =ith Uterine Aupture (Open +able in a new window*ConditionTotal CasesCases $it% Uterine Rupture&ncidencein 'atients$it% Uterine Rupture# (Yearsof Data CollectionNo.of StudiesReferencesA;nor'al pa++ern in 2e+al ear+ ra+e344 187 54 1973-2002 8Gardeil 1994, Golan 1980, &a'an 1985, /lance++e2001, 9a#lor 2002, &a%e+ 1999, -ap 2001, /)0old 2002(rolon%ed decelera+ion in 2e+al ear+ ra+e or ;rad#cardia143 114 80 1983-2002 4$iller 1994, *e)n% 1993, /)0old 2002, $enian 1998E+erine +ac#!#!+ole? or #per-!+i')la+ion30 12 40 1994-1999 2 /lance++e 2001, (elan 1998*o!! o2 in+ra)+erine pre!!)re or ce!!a+ion o2 con+rac+ion!144 6 4 1973-1999 3 Golan 1980, /lance++e 2001, ,den 1986A;nor'al la;or or 2ail)re +o pro%re!!169 49 29 1983-1996 2 &a%e+ 1999, *e)n% 1993A;do'inal pain 454 118 26 1931-2000 9Golan 1980, &a'an 1985, /lance++e 2001, -ap 2001, *e)n% 1993, $iller 1997, /)0old 2002, &odri%)e7 1989, ,den 1986>a%inal ;leedin% 381 140 37 1931-2000 8Gardeil 1994, Golan 1980, &a'an 1985, -ap 2001, *e)n% 1993, $iller 1997, /)0old 2002, ,den 1986Soc" 213 71 33 1931-1993 3 Golan 1980, &a'an 1985, ,den 1986? et al found that fetal distress was the most common finding associated with uterine rupture, occurring in !&).B&C Overall, in ' studies from 1&,-#$$$, prolonged decelerations of fetal heart rate or bradycardias occurred in 11' (&$)* of 1', cases of uterine rupture. /n cases that involved the e-trusion of the placenta and fetus into the abdominal cavity, prolonged decelerations in fetal heart rate invariably occurred.B"', &&, $, 1C;udden or atypical maternal abdominal pain occurs more rarely than fetal heart rate decelerations or bradycardia. /nstudies from 1&$-#$$#, abdominal pain occurred in 1,-"$) of cases of uterine rupture. /n a review of 1$,"! patients undergoing a +O:62, only ##) of complete uterine ruptures presented with abdominal pain and !") presented with signs of fetal distress diagnosed by continuous electronic fetal monitoring.B#C7oreover, in a study by 0u5old and ?authier, abdominal pain was the first sign of rupture in only %) of patients and occurred in women who developed uterine rupture without epidural analgesia but not in women who received an epidural block.B"'C +hus, abdominal pain is an unreliable and uncommon sign of uterine rupture. /nitial concerns that epidural anesthesia might mask the pain caused by uterine rupture have not been verified and there have been no reports of epidural anesthesia delaying the diagnosis of uterine rupture. +he 62O? guideline from #$1$ suggests there is no absolute contraindication to epidural anesthesia for a +O:62 because epidurals rarely mask the signs and symptoms of uterine rupture.3helan et al found that abnormal patterns of uterine activity, such as tetany and hyperstimulation, are often not associated with uterine rupture. /n their study, in which monitoring of uterine activity was limited to e-ternal tocodynamometry, tetany was defined as a contraction lasting longer than $ seconds, and hyperstimulation was defined as more than % contractions in 1$ minutes.B,CAodrigue> et al found that the usefulness of intrauterine pressure catheters (/U32s* for diagnosing uterine rupture was not supported. /n !" cases of uterine rupture, the classic description of decreased uterine tone and diminished uterine activity was not observed in any patients, , of whom had /U32s in place. /n addition, rates of fetal and maternal morbidity andmortality associated with uterine rupture did not differ with the use of an /U32 compared with e-ternal tocodynamometry.B&C/n & reports published from 1&$-#$$# in which investigators e-amined the fre.uency of vaginal bleeding in cases of uterine rupture, vaginal bleeding occurred in 11-"!) of cases. /n , studies, maternal shock from hypovolemia was associated with uterine rupture in #-'") of cases.B#, %, 'CDiagnosis0ecause of the short time available to diagnose uterine rupture before the onset of irreversible physiologic damage to the fetus, time-consuming diagnostic methods and sophisticated imaging modalities have only limited use. +herefore, uterine rupture is most appropriately diagnosed on the basis of standard signs and symptoms (see +able #*.@espite this limitation, various diagnostic techni.ues have been used to attempt to assess the individual risk of uterine rupture in selected patients. 6mniography, radiopelvimetry, and pelvic e-amination have all proven unsuitable for predicting the risk of uterine rupture in women who desire a +O:62. /n addition, imaging modalities such as 2+ and 7A/ have not been clinically useful in diagnosing acute uterine rupture because of the time constraints involved in establishing the diagnosis. ?iven this limitation, 7A/ is thought to be superior to2+ for evaluating the status of a uterine incision because of its increased soft tissue contrast. 6ll studies of these methods are limited by their retrospective design and their lack of surgical confirmation of true uterine dehiscence.;everal reports have suggested that transabdominal, transvaginal, or sonohysterographic ultrasonography maybe useful for detecting uterine-scar defects after cesarean delivery. Ao>enberg et al prospectively e-amined "'# women and found that the risk of uterine rupture after previous cesarean delivery was directly related to the thickness of the lower uterine segment, as measured during transabdominal ultrasonography at ,"-,& weeks of gestation. +he risk of uterine rupture increased significantly when the uterine wall was thinner than ,.% mm. Using a ,.% mm cutoff, the authors had a sensitivity of &&), specificity of !,.#), positive predictive value of 11.&), and a negative predictive value of .,) in predicting subse.uent uterine rupture.B%C/n a study of !## women, ?otoh et al reported that a uterine wall thinner than # mm, as determined with ultrasonography performed within 1 week of delivery, significantly increased the risk of uterine rupture. 3ositive and negative predictive values were !,.) and 1$$), respectively.B"C2onse.uences of Uterine Aupture"verview+he conse.uences of uterine rupture during pregnancy depend on the time that elapses from the rupture until the institution of definitive therapy. @efinitive therapy for the fetus is delivery and must generally be accomplished with alacrity to avoid ma5or fetal morbidity and mortality. 2onversely, therapy for the mother can generally be supportive and resuscitative until surgical intervention can be undertaken to arrest the often life-threatening uterine hemorrhage.;everal studies have shown that delivery of the fetus within 1$-,! minutes of uterine rupture is necessary to prevent serious fetal morbidity and mortality.B'', "', &&, 1, !C /f proper supportive measures (including fluid resuscitation and blood transfusion*, are available to treat the mother, the time for definitive surgical intervention before the onset of ma5or maternal morbidity and mortality may often be substantially longer than that for the fetus.+herefore, the conse.uences of uterine rupture may be divided into # ma5or categories, depending on whether they apply to the fetus or to the mother (see +able ,*.+able ,. Fetal and 7aternal 2onse.uences of Uterine Aupture (Open +able in a new window*Conse)uenceTotal CasesCases $it% Uterine Rupture&ncidencein 'atients$it% UterineRupture# (Yearsof Data CollectionNo.of Studies Revie*edReferences+etal or Neonatal=#po@ia or ano@ia 231 19 8 1983-2002 3 *andon 2004, *e)n% 1993, .ie!er 2002Acido!i! (E';ilical ar+er# cord p= H 7)252 83 33 1976-2002 5*andon 2004, &a8a!ia 2000, -ap 2001, *e)n% 1993, $enian 1998