Keywords
urupture - dehiscence - relative risk - cross-sectional - perinatal outcomes
Palavras-chave
ruptura uterina - deiscência - risco relativo - transversal - resultados perinatais
Introduction
Uterine rupture is defined as complete disruption of all uterine layers during pregnancy,
delivery, or immediately after delivery. It is a catastrophic situation in obstetrics,
and, although rare, often results in both maternal and fetal adverse consequences.[1]
[2]
[3] Uterine rupture can be complete or partial (dehiscence). Complete rupture usually
involves direct communication between the uterine cavity and the peritoneum, and is
associated with high rates of perinatal mortality and morbidity.[1]
[2]
[3] Dehiscence presents when the myometrium is covered by the visceral peritoneum, often
an incidental finding in caesarean deliveries, and usually described without any major
medical complications.[4]
[5]
The incidence of uterine rupture ranges between 0.5 and 5.3 per 10 thousand deliveries,[6]
[7] and mostly happens during trial of labor after a cesarian section (TOLAC).[7]
[8] Uterine rupture is also described in women without a previous cesarian section,
during spontaneous onset of labor.[9]
[10]
[11] In the Netherlands, this incidence is of around 0.007%.[10] Lower incidences were also reported in the United States (1/16,849)[12] and in the United Kingdom (0.2/1,000).[11]
The prevalence of uterine rupture tends to be lower in developed countries.[7] The risk factors include prior uterine scar[13] and the use of uterotonics.[14] Other risk factors associated with uterine rupture include inappropriate induction/augmentation
of labor, obstructed labor, previous uterine trauma, grand multiparity, abnormal placentation,
fetal anomalies, advanced maternal age, high body mass index (BMI), and lack of antenatal
care.[2]
[14]
[15]
[16]
To provide a better insight into the safety and adequacy of the current obstetrical
practice, the identification of certain risk factors becomes crucial for the improvement
of healthcare. Thus, the objective of the present study was to identify the perinatal
factors associated with uterine rupture or dehiscence in a tertiary high-risk obstetrical
care centre in Canada. Another objective was to compare these identified perinatal
factors among cases of complete uterine rupture and cases of dehiscence.
Methods
Cross-sectional study of patients with uterine rupture from January 1998 to December
2017 who were admitted at the Labor and Delivery Unit of a tertiary teaching hospital
in Canada. The code of the International Statistical Classification of Diseases, Ninth
and Tenth Revisions (ICD-9/ICD-10) was used to identify eligible patients to perform
chart reviews. All cases identified by ICD-9/ICD-10 within the 30-year period were
included. The Institutional Ethical Review Board approved the study protocol (protocol
#18–0099-C).
The clinical information obtained from the chart review included maternal age, parity,
BMI, obstetric history (including gestational age at delivery, type of previous cesarean
section incision, onset and manifestation at rupture, delivery method, maternal complications),
and neonatal outcomes (birthweight, Apgar score at 1 and 5 minutes, admission to the
Neonatal Intensive Care Unit [NICU], and stillbirth). Known risk factors for uterine
rupture, including advanced maternal age, multiparity, and TOLAC were also collected
during the chart review. The lower-segment uterine scar was defined as previous low
transverse cesarean section, while the non-lower-segment scars were those with classical
cesarean section and other uterine surgeries, either through laparoscopy or laparotomy.
Uterine rupture was defined as complete disruption of all layers of the uterus - the
endometrium, myometrium and perimetrium.[17] Uterine dehiscence was defined by incomplete division of the uterine wall that does
not encompass all uterine layers.[18] Uterine dehiscence can also cause the thinning of the uterus, often allowing the
fetus to be seen through the myometrium.[18]
The data was tabulated in Microsoft Excel 2007 (Microsoft Corp., Redmond, WA, United
States worksheets connected to the R (R Foundation for Statistical Computing, Vienna,
Austria) software, and compiled into double-entry contingency tables. The statistical
analysis was performed using Fisher Exact Test or the Chi-squared Test with Yates
correction. Associations were considered statistically significant when p ≤ 0.05. Odds ratios (ORs) were calculated between associations with Confidence Interval
of 95% (95%CI). The Student t-test was used to compare the means of parametric variables between the groups, with
results expressed as means and standard deviations. For the other variables, the simple
proportion test was used, with values expressed as a percentage.
Results
During the studied period (1988–2017), we found 174 cases of uterine disruption (0.1%;
29 complete uterine ruptures and 145 cases of dehiscence) out of 169,356 deliveries.
Cesarean section was performed for most cases of uterine dehiscence (121/145; 83%)
and uterine rupture (26/29; 90%). Among all the patients who presented with uterine
disruption (n = 174), the mean maternal age was 34 ± 4.5years, the average gestational age was
38 ± 3.3weeks, with a maternal BMI of 26.1 ± 6.7kg/m2. The mean neonatal birthweight was 3291 ± 771 g. There were no statistically significant
differences between the groups, except that pregnant women who presented with complete
uterine rupture delivered more preterm neonates compared with those who had dehiscence
(36.5 ± 4.9 vs 38.2 ± 2.9; p = 0.006).
[Table 1] outlines demographics, management and outcomes associated with uterine rupture and
dehiscence. In the demographics, there were some variables that were statistically
different between the two groups, such as multiparity (OR: 3.2; p = 0.02) and elevated maternal BMI (OR: 3.4; p = 0.02). Neither uterine rupture nor dehiscence would be predictive for diagnosing.
No associations were identified regarding complete uterine rupture or dehiscence and
maternal age, gestational age at delivery, and onset of labor.
Table 1
Associations between uterine rupture, dehiscence, and maternal and perinatal risk
factors identified during the study period
|
Variables
|
Uterine disruption
|
Odds ratio
(95% confidence interval)
|
p-value
|
|
Dehiscence
n = 145
|
Rupture
n = 29
|
Total
n = 174
|
|
Maternal age (years)
|
|
|
|
|
|
|
> 35
|
76 (44%)
|
18 (10%)
|
94 (54%)
|
1.5
|
0.34
|
|
< 35
|
69 (40%)
|
11 (6%)
|
80 (46%)
|
(0.7–3.4)
|
|
Parity
|
|
|
|
|
|
|
> 2
|
18 (10%)
|
9 (5%)
|
27 (15%)
|
3.2
|
0.02**
|
|
< 2
|
127 (73%)
|
20 (12%)
|
147(85%)
|
(3.2–1.3)
|
|
Maternal body mass index
|
|
|
|
|
|
|
> 30
|
12 (7%)
|
7 (4%)
|
19 (11%)
|
3.4
|
0.02**
|
|
< 30
|
133 (76%)
|
22 (13%)
|
155 (89%)
|
(1.2–9.5)
|
|
Gestational age at delivery (weeks)
|
|
|
|
|
|
|
< 37
|
17 (10%)
|
7 (4%)
|
24 (14%)
|
2.4
|
0.13
|
|
> 37
|
128 (73%)
|
22 (13%)
|
150 (86%)
|
(0.9–6.4)
|
|
Onset of labor
|
|
|
|
|
|
|
Spontaneous
|
36 (21%)
|
11 (6%)
|
47 (27%)
|
1.9
|
0.14
|
|
Induction
|
109 (63%)
|
18 (10%)
|
127 (73%)
|
(0.8–4.3)
|
|
Use of oxytocin
|
|
|
|
|
|
|
Yes
|
28 (16%)
|
10 (6%)
|
38 (22%)
|
2.2
(0.9–5.2)
|
0.07
|
|
No
|
117 (67%)
|
19 (11%)
|
136 (78%)
|
|
Trial of labor after cesarian section (TOLAC)
|
|
|
|
|
|
|
Yes
|
12 (7%)
|
6 (3%)
|
18 (10%)
|
2.9
|
0.05**
|
|
No
|
133 (77%)
|
23 (13%)
|
156 (90%)
|
(1.0–8.5)
|
|
Spontaneous rupture of membranes > 6h
|
|
|
|
|
|
|
Yes
|
45 (26%)
|
10 (6%)
|
55 (32%)
|
1.2
|
0.71
|
|
No
|
100 (57%)
|
19 (11%)
|
119 (68%)
|
(0.5–2.7)
|
|
Artificial rupture of membranes
|
|
|
|
|
|
|
Yes
|
77 (44%)
|
12 (7%)
|
89 (51%)
|
0.6
|
0.24
|
|
No
|
68 (39%)
|
17 (10%)
|
85 (49%)
|
(0.3–1.4)
|
|
Type of incision
|
|
|
|
|
|
|
Low transverse
|
89 (51%)
|
16 (9%)
|
105 (60%)
|
0.8
|
0.53
|
|
Classic/Other
|
56 (32%)
|
13 (8%)
|
69 (40%)
|
(0.3–1.7)
|
|
Postpartum hemorrhage
|
|
|
|
|
|
|
Yes
|
7 (4%)
|
12 (7%)
|
19 (11%)
|
13.9
|
< 0.001**
|
|
No
|
138 (79%)
|
17 (10%)
|
155 (89%)
|
(4.82–40.1)
|
|
Hysterectomy
|
|
|
|
|
|
|
Yes
|
1 (1%)
|
4 (2%)
|
5 (3%)
|
23.0
|
0.002**
|
|
No
|
144 (83%)
|
25 (14%)
|
169 (97%)
|
(2.5–214.7)
|
|
Neonate birthweight
|
|
|
|
|
|
|
> 4,000 g
|
22 (13%)
|
5 (3%)
|
27 (16%)
|
1.2
|
0.99
|
|
< 4,000 g
|
123 (70%)
|
24 (14%)
|
147 (84%)
|
(0.4–3.4)
|
|
Apgar score (at 5 minutes)
|
|
|
|
|
|
|
< 4
|
25 (14%)
|
16 (9%)
|
41 (23%)
|
5.9
|
< 0.001*
|
|
> 5
|
120 (70%)
|
13 (7%)
|
133 (77%)
|
(2.5–13.8)
|
|
Stillbirth
|
|
|
|
|
|
|
Yes
|
0 (0%)
|
9 (5%)
|
9 (5%)
|
8.2
|
< 0.001**
|
|
No
|
145 (83%)
|
20 (12%)
|
165 (95%)
|
(5.5–12.4)
|
Notes: Percentages are expressed in relation to the total number of cases (n = 174); *Pearson Chi-Square Test; **Fisher Exact Test.
Management of labor did not differ statistically in the use of oxytocin, artificial
rupture of membranes, and type of uterine incision, whereas there was a significant
association between dehiscence and TOLAC (OR: 2.9; p = 0.05). The outcomes of uterine rupture were much worse than those of dehiscence,
with postpartum hemorrhage (OR: 5.8; p < 0.001), hysterectomy (OR: 5.4; p = 0.002), and stillbirth (OR 8.3; p < 0.001). Interestingly, low 5-minute Apgar scores were more frequently associated
with dehiscence (OR: 5.9; p < 0.001).
Discussion
The present retrospective 30-year cohort described the incidence of uterine rupture
in one of the busiest hospitals in Canada. Among the charts analyzed, 83% (145/174)
of the cases were of dehiscence, and 17% (29/174) were of complete uterine rupture
with either maternal or fetal adverse outcomes associated. There were significantly
more maternal hysterectomies (5%), PPH (11%), lower neonatal 5-minute Apgar score
(23%), and stillbirth (5%) related with complete uterine ruptures.
Maternal hemorrhage, blood transfusion, and hysterectomy are the major maternal risks
associated to uterine rupture.[1]
[14]
[19] Maternal hemorrhage rates associated to uterine rupture range from 1.2% to 13.8%.[5]
[20]
[21] In our series, we identified 19/174 (11%) cases of postpartum hemorrhage (PPH),
mostly (12/174; 7%) from major ruptures with elevated OR (13.9; 95%CI: 4.8–40.1; p < 0.001). Hysterectomy was associated to uterine rupture in 5/174 (3%) cases, which
resulted in an OR of 23.0 (95%CI: 2.5–214.7; p = 0.002). Our findings were not different from those of Barger et al. (2011),[22] who evaluated severe outcomes associated with uterine rupture, including PPH and
hysterectomy in 14% of studied mothers.
We also identified an association between multiparity (> 2) (27/174 [15%]; OR: 3.2;
95%CI: 3.2–1.3; p = 0.02) and high BMI (> 30kg/m2) (19/174 [11%]; OR: 3.4; 95%CI: 1.2–9.5; p = 0.02) with uterine rupture in our series. Similar results were described by Al-Zirqi
et al. (2016),[14] who identified a 2.4-fold increase in the odds of uterine rupture in multipara (>
3). Another study[23] described that TOLACs in obesity pregnancies (BMI > 30Kg/m2) at term increase the risk of maternal (blood transfusion, uterine rupture, admission
to the Intensive Care Unit [ICU]) and neonatal complications (low 5-minute Apgar score,
NICU admission, neonatal death). Our study did not find associations between uterine
rupture and maternal age, gestational age at delivery, and membranes status, as opposed
to other studies found in the literature.[1]
[24]
Among the fetal/neonatal complications associated with uterine rupture, our 30-year
case review demonstrated elevated relative risk (RR) of stillbirth (9/174; 5%) (OR:
8.2; 95%CI 5.5–12.4; p < 0.001). The risk of perinatal death associated with uterine rupture was of 8.7%
in a population-based cohort in the Netherlands.[10] Another similar study[25] demonstrated a rate of 0.4 perinatal deaths per 1,000 associated with uterine ruptures
during a 20-year period. Several factors are associated to neonatal injury in the
context of uterine rupture, and it depends on the severity of the rupture, placenta
site, preexisting fetal comorbidities, and the degree of umbilical cord compression.[19] In our experience, all the stillbirths were associated with complete rupture, although
dehiscence was mostly associated with low Apgar scores (25/174; 14%). In a case-control
study[26] in Finland, the authors analyzed 197 cases of obstetric near-miss complications,
and, similarly to our findings, identified 8 (4%, 8/197) cases of stillbirth, all
of them consequences of uterine rupture, though the type (complete or dehiscence)
was not described.
It is unclear how accurate our statistics of stillbirth as a consequence of uterine
rupture are. The present study raised this question as we could distinguish between
a case of dehiscence and one of complete uterine rupture in our series. Regarding
the number of stillbirths out of the total cases of uterine disruption (without separation
between dehiscence and complete rupture), we found a rate of 5% of stillbirths (9/174),
similar to that of the Finnish study (4%, 8/197). Conversely, if we look at the true
stillbirth rate of uterine ruptures, it becomes 31% (9/29). A worse perinatal outcome
has been described by Berhe et al. (2015)[27] in Ethiopia (44 stillbirths/47 major ruptures; 95%). Berhe et al.'s[27] results reflected a selection of only major uterine ruptures (thus eliminating dehiscences),
and, possibly, the fact that the study was performed in a developing country. Among
the 9 cases of stillbirth in our series, 7 were due to TOLAC failure, and 2 were due
to spontaneous onset of labor with no previous cesarean sections.
A recent study[28] also from Ethiopia reinforced the importance of identifying the risk factors for
uterine rupture in specific contexts. The authors compared 135 women with uterine
rupture and 270 controls of women without uterine rupture. The risks associated with
uterine rupture were poor antenatal care (only one prenatal visit), obstructed labor,
and macrosomia. The maternal mortality rate was 9.6%, with 75% of stillbirths. Hysterectomy
was performed in 55.6% of mothers, and PPH was demonstrated in 57.8% of the cases.
Although women with previous lower-segment cesarean section who undergo induction
of labor are more likely to have uterine rupture than those with previous vaginal
deliveries,[29] this association was not found in the present study. We could not find an association
between uterine rupture and previous uterine scar or induction/augmentation of labor.
In contrast, a recent study in Denmark[9] identified the association between uterine rupture and augmentation of labor in
multiparous women. Other studies have also shown that double-layer closure of the
uterus in previous cesarean sections, compared with single-layer closure, is associated
with a thicker third-trimester lower uterine segment,[30] suggesting that the inclusion of the measurement of the thickness of the lower uterine
segment in the decision of the route of delivery[31] can reduce the rates of uterine rupture. We were not able to extract data on lower
segment thickness in this series.
We found an increased risk of uterine rupture among the patients who underwent TOLAC
(18/174, 10%), with an OR of 2.9 (95%CI: 1.0–8.5; p = 0.05), which corroborates findings already described.[29]
[32]
[33] A meta-analysis[34] evaluating women with previous cesarian sections (CSs) and the risk of uterine rupture
found that vaginal births after cesarian section (VBACs) after 2 previous cesareans
were at significantly higher risk of rupture than those with 1 previous CS (1.59%
versus 0.72%), with an overall success rate for vaginal delivery of 71.1%.
A great asset of the present study was the fact that, with our data, we could distinguish
between complete uterine rupture and dehiscence among the patients included. Our findings
contributed to reinforce the importance of the risk factors observed, while counseling
patients in obstetrical practice. Some weaknesses were associated to the cross-sectional/observational
aspect of the study. It was not possible to access the same variables among the patients
who did not present ruptures and dehiscence. Thus, the comparisons were made only
between patients who presented complete uterine rupture and those who had dehiscence.
We were not able to compare patients with complete uterine rupture and dehiscence
with those with intact uterine walls. The convenience sample used was based on the
diagnostic coding of the conditions (rupture/dehiscence), therefore only allowing
full access to the identified clinical charts. It is also important to mention that
bias could not be minimized in the present study, as data were not stratified and
multivariate analysis was not applied, due to the convenience aspect of the sample,
associated with the low prevalence of uterine rupture.
Conclusion
In summary, our 30-year analysis of uterine rupture in a Canadian population demonstrated
that there are different risk factors associated with complete uterine rupture or
dehiscence. We found that multiparity, high maternal BMI, TOLAC, low 5-minute Apgar
scores were more associated with dehiscence, whereas preterm deliveries, postpartum
hemorrhage, hysterectomy and stillbirth were risk factors more associated with complete
uterine ruptures. Even though the information we present corroborates findings already
described in literature, this is the first time that the risks are separated and compared
between complete uterine rupture and dehiscence. Our study confirms that uterine rupture
still represents a great threat to maternal-fetal health and introduces the idea that
dehiscence can also challenge maternal and perinatal outcomes.
