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References
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249
with laparoscopy-assisted local injection of etoposide. Fertil Steril. 2008;90(4):1200.e1–2.
261. Fouelifack FY, Fouogue JT, Fouedjio JH, Sando
Z.Ovarian pregnancy: a case report in a resourcepoor setting. Pan Afr Med J. 2013;16:143.
262. Ranaivoson HVR, Ranaivomanana VF,
Nomenjanahary L, Andriamampionona TF,
Randrianjasamindrakotroka NS. [Ovarian pregnancy: about 3 cases and review of the literature].
Pan Afr Med J. 2016;25:128.
263. Gray CL, Ruffolo EH.Ovarian pregnancy associated
with intrauterine contraceptive devices. Am J Obstet
Gynecol. 1978;132(2):134–9.
Uterine Rupture andPerforation
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10
Abstract
Nontraumatic uterine rupture is a rare but
often catastrophic obstetric complication
with an overall incidence of approximately
1/1536 pregnancies. In western countries, it
is ve times less common. Most spontaneous
uterine ruptures occur in women with uterine
scars, mostly due to previous Cesarean deliveries. The most consistent early indicator is
prolonged, persistent, and profound fetal bradycardia. Abdominal pain, abnormal progress in labor, and vaginal bleeding are less
consistent and less valuable in establishing
the appropriate diagnosis. Cesarean delivery
should start within 20–30 min of fetal distress. Fetal or placental extrusion through the
uterine wall mostly results in irreversible
fetal damage. Therefore, such a recommendation is of limited value in preventing major
fetal and neonatal complications. However,
immediate supportive and resuscitation
methods within this period prevent maternal
exsanguination and death. This is followed
by denitive surgical intervention. Traumatic
uterine rupture mostly results from maternal
blunt abdominal trauma. Pathophysiology is
similar to nontraumatic rupture. Uterine perforation is rare. It results from maternal stab
or gunshot wounds.
Ruptures occur during the increased pressure on
the organ, either from outside or inside. Ruptures
can be spontaneous or traumatic. Perforation
occurs when the underlying pathologic process
destroys or penetrates the organ wall.
10.1 Spontaneous Uterine
Rupture
10.1.1 Historical Perspective
One of the rst descriptions of spontaneous uterine rupture (UR) was by Wilhelm Fabry (also
William Fabry, Guilelmus Fabricius Hildanus, or
Fabricius von Hilden) in the seventeenth century
(Fig.10.1). The rst case was a multigravida during labor at term with the UR due to fetal transverse lie. The second was a fatal case of UR
caused by obstructed labor [2]. In James Dowling
Trask’s (1821–1883, one of the founders of the
American Gynecologic Society) monograph on
UR, 303 cases were recorded from 1700 to 1848;
only 38 were classied as URs during pregnancy,
the others being cases of UR during labor. Real
numbers are smaller when cases are excluded
that are some other condition or premature labor.
When this reduction has been made, 14 cases
remain [3]. Cooper, in 1858, described the postmortem ndings of UR, in the third month of
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
G. Augustin, Acute Abdomen During Pregnancy, https://doi.org/10.1007/978-3-031-26021-6_10
251
252
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Fig. 10.1 Wilhelm Fabry (June 25, 1560–February 15,
1634), often called the “Father of German surgery,” was
the rst educated German scientic surgeon. He is the
author of 20 medical books. His Observationum et
Curationum Chirurgicarum Centuriae, published posthumously in 1641, is the best collection of case records of
the century. (Reproduced with permission from [1] under
the CC Attribution License)
10 Uterine Rupture andPerforation
pregnancy, from tuberculous degeneration of the
fundus [4]. A further collection of 98 UR cases
was by R.P. M.Ames (the Philadelphia Hospital
and the Jefferson Medical College Hospital,
Philadelphia) in 1881 [5] and A. Lewers (17
cases) in 1887 [6]. In 1903, Baisch recorded 37
nontraumatic URs in the rst 6months of pregnancy [7].
10.1.2 Denition andClassication
UR is a disruption of the uterine muscle and visceral peritoneum or a uterine muscle separation
extending to the bladder or broad ligament. UR
can be incomplete or complete.
Incomplete (partial) uterine rupture is present
when the uterine wall is extremely thinned, and
the uterine muscular layer is lost, but the uterine
serosa (parietal peritoneum) is preserved
(Fig. 10.2). One example is the laceration that
opens from the uterus into the broad ligament but
with the anterior and posterior leaves of this
structure remaining untorn. Incomplete UR is
common with scar dehiscence. In contrast to a
frank UR, uterine scar dehiscence disrupts and
separates a preexisting uterine scar after
CS.Uterine scar dehiscence is a more common
event than UR.Importantly, the defect in the uterine wall limited to scar dehiscence does not disrupt the overlying visceral peritoneum. It does
Fig. 10.2 Operative ndings at a Cesarean section. (a)
The thin anterior uterine wall (asterisk) with a bulge
caused by fetal parts from the inside. Arrows indicate the
peritoneum. The left side of the photograph is the caudal
side of the patient. (b) After delivery and removal of the
placenta, the thin wall is gently pushed from inside the uterus
with a nger. The ngertip (large arrow) is visible through
the thin wall. The asterisk indicates the surgeon’s right hand.
Small arrows indicate the uterine incision site. (Reproduced
with permission from [8] under the CC BY 2.0)
10.1 Spontaneous Uterine Rupture
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not result in clinically signicant bleeding from
the edges of the preexisting uterine scar. In addition, in cases of uterine dehiscence (as opposed
to UR), the fetus, placenta, and umbilical cord
remain contained within the uterine cavity.
Complete uterine rupture is present when rupture occurs through all layers of the uterine wall,
including serosa with or without accompanying
bleeding or hematoma (Fig.10.3). Therefore, the
amniotic cavity directly communicates with the
abdominal cavity. Approximately 70% have a
complete UR and 25% have an incomplete
UR.Seventy percent of scar ruptures presented
with complete UR [10].
Additional factors dictate treatment strategy
and prognosis: (1) placental abruption, (2) the
expulsion of the fetus into the abdominal cavity,
or (3) the expulsion of the amniotic sac (Fig.10.4).
Several classication systems are related to UR
etiology. The main classication is traumatic UR,
spontaneous UR [12], or a combination of these.
True spontaneous UR is a partial or full- thickness
separation of the uterine wall before the onset of
myometrial contractions that occurs primarily in
the third trimester when the intrauterine volume
and pressures are at the highest levels. Unfortunately,
253
Fig. 10.4 Intraoperative appearance of the uterine fundus
before placenta removal. Uterine rupture is at the right corneal area with prolapsed amniotic sac (*). (Reproduced with
permission from [11] under the CC Attribution License)
many cases were published under the term spontaneous but are not true spontaneous URs.
Schrinsky and Benson made an etiologybased classication in 1978 [13], which was further updated and expanded (Table10.1).
Rickards, in 1938, described ve types of UR
of the scarred uterus during pregnancy [17].
Type I the rupture occurs through an old upper
segment incision, and the placenta is situated
away from the uterine scar. Characteristics
include the following:
• The rupture tends to take place during labor,
• Little or no bleeding with a normal pulse,
• The pain may become niggling in type after
the scar has started to give way,
• The bulging bag of membranes may some-
times be palpated through the abdominal wall,
• Prognosis is good, provided that suitable treat-
ment is available.
Fig. 10.3 Complete uterine rupture with a large left
broad ligament hematoma with multiple minor bleeding
points from the branches of the uterine artery. (Reproduced
with permission from [9] under the CC BY 3.0)
Type II The rupture occurs through an upper
segment incision, and the placenta is underneath
the old scar. This type is more severe. When the
placenta is underneath the old scar, the placental
villi gradually erode brous tissue [18]. This erosion is insidious and may cause marked attenuation of the scar during the latter part of pregnancy.
The rupture is more liable to occur before the
onset of labor. The eating away of the scar may
be associated with vague pains in the lower abdomen [19]. As the process is gradual, hemorrhage
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10 Uterine Rupture andPerforation
Table 10.1
during pregnancy [13–16]
1. Traumatic rupture
(a) Instrumental
Uterine sound or curette
Manual removal of placenta
Various tools for legal or criminal abortion
(b) Violence: direct or indirect
(c) Obstetric
Oxytocins, forceps, breech extraction
Intrauterine manipulation: internal version,
Fundal pressure
Hydrocephalus
Neglect: cephalopelvic disproportion, transverse
2. Spontaneous rupture
(a) Previous uterine surgery
Cesarean section (scarred uterus)
Myomectomy
Salpingectomy
Ventroxation
Curettage or manual removal of the placenta
(b) No previous surgery
Congenital uterine abnormality
Cornual pregnancy
Hydatidiform mole or chorioadenoma destruens
Placenta percreta
Genetic susceptibility for rupture (Loeys–Dietz
Red degeneration of broid
Chronic corticosteroid use
IVF?
No apparent cause
3. Combinations
Orgasmic uterine contractions
Classication of causes of uterine rupture
forceps rotation, shoulder dystocia
lie
syndrome)
is seldom severe. Characteristics include the
following:
• Gradual rupture tends to occur toward the end
of pregnancy. This may be accompanied by
vague pain in the lower abdomen,
• After the onset of labor, bleeding may be of
considerable severity,
• Prognosis will not be as favorable as type I
and will depend mainly on the amount of
intra-abdominal bleeding.
Type III The rupture occurs after a previous
lower segment CS. Characteristics include the
following:
• Rupture takes place during labor,
• Hemorrhage may occur due to the extension
of the laceration laterally into the uterine
arteries,
• The bladder may be involved, giving rise to
hematuria.
Type IV The rupture is complete through an upper
segment incision, and the child, within its bag of
membranes, is expelled into the abdominal cavity,
the placenta remaining in situ. The uterine scar separates, the contractions persist, and the child is
extruded into the abdominal cavity. The fetal heart
sounds almost invariably disappear, and fetal movements cease. The uterus is pushed over to one side,
and the child, oating in the abdominal cavity, is
palpable. Characteristics include the following:
• Fetal heart sounds cease as a rule,
• Fetal movements usually stop,
• The uterus is pushed to one side,
• The fetus, lying free in the abdominal cavity,
is easily palpable.
Type V The rupture is complete through an
upper segment incision, and the child, with its
placenta, is extruded completely into the abdominal cavity. Characteristics include the following:
• Often associated with severe intra-abdominal
hemorrhage,
• Fetal heart sounds are absent,
• Fetal movements are absent,
• The uterus is pushed over to one side,
• The fetus, lying free in the abdominal cavity,
is easily palpable.
10.1.3 Mechanisms
10.1.3.1 Scarred Uterus
Uterine Scar Rupture
Patients with uterine scars are more likely to have
uterine scar rupture due to the attempted trial of
labor and inadequate labor monitoring [20]. Most
uterine dehiscences and ruptures in scarred uteri
will occur via the uterine scar. The atrophic, inelas-
10.1 Spontaneous Uterine Rupture
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tic nature of the scar renders it less adaptive to forces
in labor, predisposing it to rupture. Prostaglandins
induce local biochemical modications that weaken
the scar, predisposing it to rupture [21]. In the trial
of labor, secondary inertia may indicate that a partial or complete UR has interfered with the mechanism of labor. The blocking of the neuromuscular
impulses is caused by the break in the continuity of
the muscle [22]. In women with scarred uteri, catastrophic complete prelabor UR occurred mainly in
scars outside the lower segment [23].
Atypical Site Rupture
A particularly rigid anterior lower segment may
cause the abnormal distribution of force. The
posterior wall may be excessively shortened and
thinned during retraction due to the rigid anterior
uterine scar, catalyzing atypical UR via healthy
tissue. Any factor compromising uterine structural integrity or causing abnormal force distribution can precipitate UR. The site of UR is
unpredictable and may be atypical.
The lower segment UR is the most common
(60%) site of rupture [24–27], with the anterior
transverse location being the most common [28].
The second most common location is an extension
to the broad ligament, and other locations have an
incidence of around 5% [28]. Mostly there is no
differentiation between UR caused by obstructed
labor and scarred uterus. UR is complete in around
73% of cases and incomplete in 27% [24, 25, 27].
Posterior (posterolateral) UR complicating
vaginal birth after low-transverse CS is rare [29–
33]. Fetal malposition with an occipitoposterior
position contributes to posterior UR (Fig.10.5),
as does malpresentation with a transverse lie [32,
33]. Malposition alters the distribution of con-
tractile force and increases labor dystocia;
certain malpresentations cause uterine hyperdistension, which may precipitate atypical
UR. Prostaglandins generate excessive uterine
activity increasing the UR rate. Prostaglandins
may cause excessive uterine activity, resulting in
a posterior wall sacculation of a strong anterior
scar [31]. During the second stage of labor, with
the fetus undergoing cardinal movements, UR
occurs through the weakened posterior wall. In
50%, prostaglandins induced labor, suggesting
255
Fig. 10.5 Vertical posterior rupture of the scarred uterus
due to the occipitoposterior position of the fetus.
(Reproduced with permission from [32])
other factors may play a role [33]. An inelastic
scar comprising brous tissue on the anterior
wall prevents the even distribution of contraction
forces. As uterine muscle retracts during the
active phase of labor, the healthy posterior wall
may undergo excessive shortening and thinning
compared to an inelastic anterior wall, which
could predispose to rupture.
10.1.3.2 Unscarred Uterus
Obstruction as a cause of UR and the delay in
accessing qualied care is found in developing
counties with patients without antenatal care. The
causes of UR during labor result from obstruction of vaginal delivery, whether the obstruction
is a pelvic contraction, unusual size of the child,
or malpresentation. The uterus continues to contract, with thickening of the upper part, while its
lower segment becomes thinned. Without assistance, the lower segment becomes increasingly
thinned and nally ruptures.
The rupture of the unscarred uterus during
labor almost always begins in the lower
segment.
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10 Uterine Rupture andPerforation
A uterus emptied of its contents by their extrusion into the peritoneal cavity may retract rmly,
preventing bleeding from the placental site and
the wound in the uterus. The fetus and placenta
do not necessarily escape at once or at all. It is the
most common cause of spontaneous UR, ranging
from 68.5% to 73.2% [20, 34] in developing
countries. In developed countries, it is signicantly lower, starting from 13% [35].
10.1.3.3 Simultaneous Uterus
andBladder Rupture
Simultaneous spontaneous UR and bladder rupture are common due to the same mechanism and
location of obstruction and distension (see Sect.
28.3). It is more common with ruptures of uns-
carred uteri, which extend beyond the cervix [36].
10.1.4 Incidence
10.1.4.1 Developed vs. Undeveloped
Countries
The rate of spontaneous UR during the last
50years in developed countries has been increasing [37]. Table10.2 shows the differences in inci-
dence between countries. Preterm UR in the
unscarred uterus is extremely rare in developed
countries but is rising (1/333.333) [23]. In the
developed countries, in the scarred uterus, there
is a similar incidence of complete ruptures
(1/5556), partial ruptures (dehiscences) at elective CS (1/5556), and partial ruptures at emergency prelabor CS (1/5263) [23].
Several issues arise with obtaining a true incidence. First, especially in Africa, registration of
births occurring at home is incomplete, although
the number of patients who deliver at home and
only seek medical attention when problems occur
decreases. Second, some maternal deaths occur
in rural areas before hospital admission without
known and registered causes of death. There are
also signicant differences between regions in
the same country. The incidence of 1/167–1/200
deliveries was found in Southwest Nigeria [42,
43, 72], while in Northwest Nigeria was more
than double (1/77 deliveries) [46, 47]. Third,
because the health reforms policy of the govern-
Table 10.2 (Spontaneous) uterine rupture rates across
the world (in decreasing incidence)
Country Incidence
Ethiopia [34, 38] 1/38–1/175
Uganda [20, 39] 1/93–1/200
Pakistan [40] 1/100
Yemen [41] 1/159
Nigeria
Southwest [28, 42–44] 1/186–1/416
Rural [45] 1/112
Northwest [46, 47] 1/77
Guinea [48] 1/199
Morocco [49] 1/222
Sudan [50] 1/246
India [51, 52] 1/357–1/714
Kenya [53] 1/425
Libya [54] 1/585
Iraq (Basra) [55] 1/801
Turkey [56] 1/966
Saudi Arabia [57] 1/1011
Nepal [10] 1/1100
Australia [58] 1/1163
Zimbabwe [59] 1/1285
Rep. of South Africa [60] 1/1362
Trinidad [61] 1/1500
Netherlands [62] 1/1695
Bahrain [63] 1/2213
Tunis [14] 1/2581
Kuwait [64, 65] 1/1851–1/3333
Israel [66] 1/2802
Canada [67] 1/3333
Taiwan [68] 1/3871
Ireland [69] 1/4348
Qatar [70] 1/4968–1/6843
Singapore [71] 1/6331
United States [12] 1/8000–1/15,000
Norway [36] 1/10,000
ment in many countries prohibits refusal of
admission of any medical emergency in all the
receive many labor complications that occur in
the primary and secondary health facilities and
private hospitals. Therefore, the accurate incidence distribution among hospitals is not known.
Fourth, some studies report cumulatively spontaneous (scarred and unscarred uterus) and sometimes traumatic URs [43]. Reports from Nigeria,
Ghana, Ethiopia, and Bangladesh indicated that
about 75% of UR cases were associated with the
unscarred uterus [73], while in Norway, UR associated with the unscarred uterus is 33% [36].
3.0
29000
Number of deliveries per year
Ruptured uterus rate per 1000 deli.
Year
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257
For developed countries, the available data
indicate that the prevalence of UR for women
with previous CS is 1%, whereas it is extremely
rare for women without previous CS (<1/10,000).
Overall, the rates are below 1/1000 [74].
10.1.4.2 Decade Dependency
The incidence is decade-dependent. The incidence of UR in the US between 1967 and 1978
was 1/1000–1/1500 deliveries, but spontaneous
UR accounted for 25%, and only 17% of these
occurred before the onset of labor [15]. After two
decades, spontaneous rupture of the unscarred
uterus ranged from 1/8000 to 1/15,000 deliveries
[12, 75]. Due to the rarity of spontaneous UR,
most studies have a study interval of around a
decade to collect enough patients for analysis and
comparison. With the progress of medicine and
knowledge of the risk factors, the incidence is
decreasing, but there are still signicant differences between developed and undeveloped/
developing countries (Fig.10.6).
10.1.5 Risk Factors
Most spontaneous UR in undeveloped/developing countries is due to rupture of the unscarred
uterus secondary to neglected obstructed labor. In
contrast, CS scar/scarred uterus is the most common cause in developed countries [72]. In developed countries, the rupture of the unscarred
uterus is several fold lower than that of scarred
uterus involving 1/17,000–1/20,000 deliveries
[24].
Some recommend a continuous infusion of
tocolytics to prevent UR with risk factors present
[77].
10.1.5.1 Scarred Uterus
Eardley Holland, in 1920, made the rst overview
and found that 4% of Cesarean scars give way
during a subsequent pregnancy or labor [78].
Previous CS is the most important predisposing
factor for the occurrence of UR [79], and the socalled scarred uterus (uterine scars from any type
of CS) is present in up to 65% of cases [57, 80]. It
is conventionally attributed to the structural compromise of the uterine scar, as depicted by the
term “trial of the scar.” The rate of CS has risen
from 5% in 1970 to 26% in 2002 despite improvement in nonoperative obstetric procedures [81].
Relevant to vaginal birth after CS (VBAC) in the
USA is its increasing rate, from 3.4% in 1980 to
28% in 1996. With an eightfold increase in the
VBAC rate, maternal and perinatal morbidity also
increased, particularly UR.By 2007, the VBAC
rate in the USA had fallen to 8.5%. The CS rate
Fig. 10.6 Comparison
of the total number of
deliveries in 1970–1973
and 1980–1983 with the
rate of ruptured uterus
per 1000 deliveries in
those years in South
Africa. The numbers for
1983 are a multiplication
of the rst 6months.
R.U. rupture of the
uterus. (Reproduced
with permission from
[76])
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
1970
1980
No. of de
at
R
of del.
No.
l
e o
1971
1981
.
f
80-8
R
7
3
.U. 70-
0-83
7
28000
27000
26000
25000
3
R
a
t
e
o
f
R
.
U
.
80
-
8
3
1972
1982
1973
1983
24000
23000
22000
21000
20000
19000
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10 Uterine Rupture andPerforation
also reached an all-time high of 32% in 2007. In
its recent guidelines on VBAC, the American
Congress of Obstetricians and Gynecologists
(ACOG) adopted the recommendation not to
restrict women’s access to VBAC [82]. This
occurred after the National Institutes of Health
Consensus Development Conference Panel
reviewed the totality of the evidence concerning
maternal and neonatal outcomes relating to VBAC
[83]. UR affects 0.7–1.9% of women with previ-
ous CS attempting a trial of labor [84]. The
reported recurrence rate for UR is 4.8–19%, with
the highest rates seen in women with a history of
a ruptured upper uterine segment (classic scar). In
these cases, planned CS is recommended [85].
Classic Cesarean Delivery
Classic CS via vertical midline uterine incision is
currently infrequently performed and accounts for
0.5% of all births in the USA [86]. There is an
11.5% absolute risk of UR in women with classic
vertical CS scars who underwent an unplanned
trial of labor after CS (TOLAC) [87]. The UR rate
for women with prior classical uterine CS scars
was 0.64% for women who underwent repeat
CS.All patients underwent repeat CS, but a high
rate of preterm labor resulted in 49% being in
labor during CS [86]. An absolute UR rate in
women with a previous classic, inverted T, or J
incision presented in advanced labor or refused
repeat CS was 1.9% [88]. These rates of frank UR
in women with classic CS contrast with the higher
rates of 4–9% that the ACOG had historically
reported for women with these types of uterine
scars [89]. However, there is a 9% rate of asymptomatic uterine scar dehiscence [86]. This suggests
that disruptions of uterine scars might have been
misclassied as true UR instead of dehiscences.
Low-Vertical Cesarean Section
There is a 1.1% absolute risk of symptomatic UR
in women undergoing a TOLAC with a lowvertical CS scar [88, 90]. Compared to women
with low-transverse CS, there is no signicantly
increased risk of UR or adverse maternal and
perinatal outcomes. Inconsistencies hamper the
interpretation of how high the lower uterine segment could be cut before it was considered a clas-
sic incision. Even when the lower uterine segment
is already well developed due to active labor, a
low-vertical incision of adequate length is often
impossible to permit fetal delivery. The classic
extension is arbitrarily dened as a 2cm extension into the upper segment, and the overall rate
of UR was 0.62%. This rate could be further
divided as 1.15% for women who underwent a
TOLAC compared with no UR among women
who underwent elective repeat CS [90].
Unknown Uterine Scar
In many instances, the type of incision used for a
prior CS cannot be conrmed due to the unavailability of the operative report. Under these circumstances, the assessment of UR risk may
sometimes be guided by the obstetric history to
infer the most probable type of uterine scar. For
example, a patient with a history of a preterm CS
at 28weeks’ gestation has a much higher likelihood of having had a vertical uterine incision than
a patient who underwent a CS to indicate the
arrest of fetal descent at term. Probably because
most CS in the USA is accomplished via lowtransverse uterine incisions, the risk of UR with
an unknown scar and previous low-transverse
hysterotomy is similar. This logic depends on the
high ratio of low-transverse to vertical incisions
performed for CS.However, it ignores the varying
probability that different types of uterine incisions
are made under different obstetric circumstances
and differences due to varying medical resources
and the prevailing local practitioner practices in
countries other than the USA. An estimated
20,000 African refugees enter the USA each year,
80% from countries where the upper uterine segment CS is not an uncommon practice. The immigration of African refugees to Europe is becoming
increasingly common. Nevertheless, most CS
performed in the USA is accomplished via lowtransverse uterine incisions.
Underpowered small case–control studies did
not nd an association between an unknown
uterine scar and UR risk [91, 92]. The Maternal-
Fetal Medicine Units Network Cesarean Delivery
Registry reports a 0.5% risk of UR for patients
who underwent a TOLAC with an unknown uterine scar [88]. A small, randomized, controlled trial
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259
compared labor augmentation with oxytocin with
no intervention in women with prior CS involving
either one or two unknown uterine incisions. All
uterine dehiscences and UR occurred in the group
that underwent labor augmentation [93].
Low-Transverse Cesarean Section
The myometrium from the scarred low uterine
segment has a higher collagen content than the
unscarred myometrium from laboring women but
not unscarred myometrium from nonlaboring
women [94]. The UR risk after a low-transverse
CS varies depending on whether patients undergo
a TOLAC or an elective repeat CS, whether labor
is induced or spontaneous, and other factors.
Today, the vast majority of CS is of the lowtransverse type. Examining the various risk factors for UR is instructive for women with one
previous CS. CS has potential complications,
including an increased risk of placenta previa and
accreta with every subsequent repeat CS, resulting in higher rates of peripartum hysterectomy
[95]. The trend of an increasing rate of UR with
increasing maternal age was noted [96, 97]. Agerelated decreases in myometrial strength [98] and
defective wound healing [99] could contribute.
Cesarean Section Without aSubsequent
Trial ofLabor
The spontaneous UR rate among women with a
single CS scar who underwent scheduled repeat
CS without a TOLAC is 0.16% [100]. The uteri
with CS scars have an intrinsic propensity for the
UR that exceeds that of the unscarred organ during pregnancy, which is 0.012% (OR 12).
Therefore, all other UR rates in women with a
previous CS should be referenced to this expected
baseline rate.
Cesarean Section withSubsequent
Augmentation ofLabor
There is a wide variance in the frequency of clinical
use of oxytocin and the dose and dosing schedules.
As a result, there is a paucity of specic evidencebased clinical guidelines for using oxytocin in
VBAC trials. UR rate in women who underwent
oxytocin augmentation of labor after a previous CS
was 0.9–1.4%, compared with 0.34–0.4% in women
who underwent a trial of spontaneous labor (twofold to fourfold increased risk) [83, 102]. Others
claim that labor augmentation with oxytocin does
not increase the risk for UR in the scarred or unscarred uterus [101, 103]. However, the conclusions
to be drawn from this are both limited. Therefore,
the duration of labor and not oxytocin use itself may
predispose the patient with or without a uterine scar
to rupture. The problem in some studies from developing countries is the high percentage of its use;
41.7% of the respondents were given this drug (all
but one had it through IV infusion) [41]. Oxytocin
was used to augment prolonged and obstructed
labor rather than for active labor management, concluding that supervision and control over this drug
are missing. In this regard, assessing the safety of
oxytocin use in VBAC trials must consider both the
dosage and exposure time. At an intravenous oxytocin dosage range of 6–20 mU/min, a more than
threefold increased risk of UR was associated with
oxytocin use. At a dosage range of more than
20mU/min, a nearly fourfold increased risk of UR
was noted. The attributable risk associated with
oxytocin use was 2.9–3.6% for the maximum oxytocin dose ranges of more than 20 mU/min and
more than 30mU/min. There was no signicant risk
association between time (in terms of both duration
of oxytocin exposure and duration of labor) and UR
risk [104].
Cesarean Section withSubsequent
Spontaneous Labor
The UR rate among women with a single previous CS who labored spontaneously during a subsequent singleton pregnancy is 0.45–0.72% [100,
101]. This rate of UR implies an increased rela-
tive risk of 3–4 for women who labor spontaneously compared with women who undergo
elective repeat CS.
The upper limit of 20mU/min of oxytocin
for use in VBAC trials is recommended
with monitoring of oxytocin for both labor
augmentation and induction.
Newer studies claim that labor induction and
augmentation of labor have similar UR risks
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