Interpretation
Uterine rupture in pregnancy is rare, but when it occurs the
consequences can be life-threatening to both mother and fetus13, 14. The occurrence of uterine rupture varies in
different parts of the world. Globally, the incidence of uterine rupture
is 0.07% with the tendency of being lower in developed countries than
developing countries1 15. The rate
of uterine rupture in our study was 0.0196%, consistent with the rate
of developed countries. There were no cases of maternal death due to
uterine rupture in our study.
There has been wide variation in the aetiology uterine rupture over
years16-18 , where the increase rate of TOLAC and the
use of uterotonics have created the two most common predisposing factors
in the developed countries9, 15, 19, 20. However, the
major causes of uterine rupture in developing countries are both
obstetric and non-obstetric multitude of factors: multi-gravidity,
teen-age pregnancy, old primi, poor socio-economic status, previous
cesarean section scar, unsupervised labor and unwise use of uterotonic
agents4.
Our study showed that the key risk factor of uterine rupture was the
presence of scar, and previous cesarean section is the most important
cause of uterine scarring. Therefore, to reduce uterine rupture rate, we
need to strictly control the indication of cesarean section so as to
reduce the rate of cesarean section. Globally, cesarean delivery rates
have been steadily increasing over the past 20-30
years21-23. A major contributor to this has been
elective repeat cesarean sections. Approximately one-third to half of
elective cesareans are performed because of a history of cesarean
delivery21, 24, 25. Routine elective repeat cesarean
section for all women with a prior cesarean section is not universally
advocated, desired, or without risk. Furthermore, multiple cesarean
sections also carry the increased risk of placenta previa and placenta
accrete with future pregnancies26. And such a policy
would result in significant financial cost 27.
However, VBAC limited such problems. As another mode of birth after
caesarean section, VBAC is associated with fewer complications, such as
shorter maternal hospitalization, less blood loss, and a decreased
incidence of puerperal infections and thrombotic
events28. TOLAC is a safe option for most people and
75% women may be successful29.Recent years, VBAC has
been supported as a way to decrease related complications and slow the
increase in cesarean births to some extents. In Norway, all mothers with
one previous caesarean section are offered a chance of TOLAC unless
there is an absolute contra-indication. The TOLAC rate is high with
51%, and 80% succeed30. VBAC is being advocated by
more and more countries, but in China, the VBAC rate was only 9.6% in
2016, as compared to 12.4% in the United States in the same
year31, 32.While TOLAC is accepted practice in
hospitals with advanced medical equipment and obstetric skills, it is
still controversial. A successful VBAC is associated with fewer
complications compared with elective repeat cesarean delivery, whereas a
failed TOLAC is associated with more complications33.
We can see TOLAC has gone through three stages in US. Stage one, VBAC
rates had increased from 5% in 1985 to 28.3% by 1996 as
recommendations favored TOLAC; Stage two, the VBAC rate had decreased to
8.5% by 2006 as the number of uterine rupture and other complications
related to TOLAC increased. Some hospitals stopped offering TOLAC
altogether; Stage three, VBACs had been on the rise again since 2016 and
increased to 13.3% by 2018, when a balance between TOLAC and safety was
reached32, 33. U.S. experience is worth learning and
most part of China is going through the stage two, so we can see the
reversal of the VBAC. Therefore, promoting TOLAC in China and
ensuring the safety is needed. In
our study, we were expecting uterine rupture rates to be higher as
people attempted a TOLAC increased. However, this was not the case here
and ruptures occurring after TOLAC were not more serious. Our hospital
is one of the three hospitals with the largest number of births in
China, and Shanghai is one of the most advanced medical treatment areas
in China, which is close to developed countries, so we have rich medical
experience to reduce the occurrence of uterine rupture and ensure the
maternal and perinatal safety. Our study provides evidence that under
the condition of strict control and indication, TOLAC is safe and
reliable and worth carrying out. With the implementation of the policy
of encouraging birth in China, more and more second-child pregnant women
choose to attempt a TOLAC, the rate of cesarean section and consequent
risk of uterine rupture will decline as a whole, and the national
medical burden and financial expenditure can be reduced.
The other two causes of uterine scarring in our study are previous
myomectomy and previous cornual pregnancy. All our cases with a previous
myomectomy surgery were performed by laparoscopy. With the rise of
minimally invasive techniques, laparoscopic surgeries are being
performed in greater numbers today than ever before. Despite
overwhelming evidence that laparoscopic myomectomy is minimally invasive
and associated with fewer perioperative complications, there is one
concern that is still under debate, i.e., does laparoscopic myomectomy
increase risk of subsequent uterine rupture? Some previous studies
showed there was no difference between laparoscopic and open myomectomy
on the risk of uterine rupture while others demonstrated that
laparoscopic procedure increased this risk compared to open approach
because it was believed to result in incompletely repaired muscle
defects34-37. The use of powered instruments, limited
instrumentation use and impossibility of palpation might be the reasons.
Some techniques including multi-layer closure of the myometrium and
limited use of electrosurgical energy should be adhered to by surgeons
to decrease the risk37. In our study, it seems to lead
to more serious outcomes regarding the 6 uterine rupture cases following
laparoscopic myomectomy. Among them 4 had excessive blood loss above
2000 ml and presented signs of hemorrhagic shock, 3 had the worst
outcome, i.e., the fetuses did not survive. They might even be
influenced by long-term sequelae, which can adversely affect subsequent
pregnancies. The removed myoma size and number in uterine rupture
patients were within average range of normal cases of laparoscopic
myomectomy, which is consistent with other studies37,
38.And there is no evidence indicating the best contraception period
prior to pregnancy after myomectomy to avoid uterine rupture. Currently
this interval varies by facility 34.Some suggested 12
months might be adequate while others concluded there was no safe
interval34, 38, 39. In our study, the only UR case
without serious complication after laparoscopic myomectomy had an
interval for 9 years, which is the longest. Thus, it seems to keep the
duration of the contraception period longer will be safer for patients
with a history of laparoscopic myomectomy. Therefore, clinicians must
remain vigilant, particularly in patients with a history of laparoscopic
myomectomy. And whatever the cause of scar uterus, special monitoring is
needed during pregnancy and childbirth to ensure the health of the
mother and newborn.
In contrast to uterine ruptures in women attempting TOLAC, the uterine
rupture in women with unscarred uteruses occurs often completely
unexpectedly. We found an incidence of uterine rupture among women with
no previous uterine scar was 3/209112 deliveries, which was in agreement
of the incidence found by Thisted et al based on data from the Danish
Medical Birth Registry20. All three uterine rupture
cases in our study were uncompleted uterine ruptures found during the
cesarean section with almost the same maternal and fetal complications
rates as scarred uterus. Among them, two (2/3) were multiple pregnancy
with uterus contraction before the cesarean section, one fell to birth
vaginally because of obstructed labour. Our findings suggest that
multiple pregnancy and obstructed labour are two major risk factors for
uterine rupture in patients without a history of previous uterus
surgery, which is in line with the recent reports published by Gibbins
et al, Vandenberghe et al and Vilchez et al 40-42.
Timely detection of uterine rupture is conducive to improving maternal
and infant outcomes. Symptoms are the only indicators that change
dynamically, which can provide first-hand information for the doctors.
In the past, caregivers were taught to look for classic signs such as
sudden tearing uterine pain, vaginal hemorrhage, cessation of uterine
contractions, Bandl’s ring and regression of the
fetus43, 44. However, some studies have shown that
these signs are not specific and often absent43, 45.
Our study shows that the change of the fetal heart rate is the most
reliable presenting clinical symptom. Most of the cases also presented
with abnormal pain and vaginal bleeding. Alertness to these signs is the
key to the timely rescue and successful management. Other studies have
the same conclusions consistent with ours43, 45.
The most common site of rupture was in the lower uterine segment (58.5
%) in our study, which was the scar site of the previous cesarean
section. This result is consistent with the findings of the study done
by Rizwan et al4, in which 80 % of the rupture was
observed in the lower uterine segment.