3.3.9 Cesarean section rate
Four studies were included for this analysis[10,11,16,17]. Due to significant heterogeneity
across studies (P =0.33, I 2=66%), a
random-effect model was used. Meta-analysis did not find any significant
difference in cesarean section rate between the two groups
(RR =1.02, 95%CI : 0.72 to 1.44, P =0.93) (Figure
1-10).
3.4 Publication bias
A funnel plot was used to detect potential
publication bias for the outcome of
premature birth rate before 34 weeks. As pictorially shown in Figure 2,
the funnel plot was symmetric on visual inspection, indicating a low
risk of publication bias.
4. Discussion
Preterm birth is one of the most important determinants of perinatal and
infant mortality and morbidity worldwide, which is among the most
complex challenges to modern obstetrics. Spontaneous preterm birth is
estimated to be responsible for roughly 28% of the world’s 4 million
annual neonatal deaths[18]. Decreasing the
incidence of spontaneous preterm birth is critical to reduce perinatal
and neonatal mortality and morbidity. The onset and delivery of preterm
labor is similar to that of full term, but the exact mechanism remains
unknown. Short cervix syndrome, also known as cervical shortening, is
considered as a strong predictor of preterm
birth[19]. For pregnant women with a prior history
of preterm birth or shortened cervix, secondary prevention based on
proper management of a short cervix has been shown to reduce the risk of
preterm birth[19].
However, the published studies on the use of cervical pessary versus
cervical cerclage to prevent short cervix-related preterm birth are
limited by their small sample size, and these studies reported
conflicting findings. There is a lack of meta-analysis comparing
cervical pessary with cervical cerclage in the management of preterm
birth associated with a short cervix. Therefore, this study
systematically reviewed the published RCTs and non-RCTs on the efficacy
and safety of cervical pessary versus cervical cerclage in preventing
spontaneous preterm birth, in order to offer more effective options for
pregnant women with a short cervix who are at a risk for preterm birth.
Our results indicated that compared with cervical cerclage, use of a
cervical pessary significantly decreased the incidence of PPROM and
premature birth rate before 34 weeks. But other endpoints including
premature birth rates before 28, 32 or 37 weeks, cesarean section rate
as well as neonatal outcomes were similar between the two groups.
We acknowledge that this study has several limitations: 1) Only 2
non-blinded RCTs were included, which are subject to potential selection
bias and measurement bias. 2) One study was conducted in twin
pregnancies while others were performed in singleton pregnancies. 3)
Seven of the included studies used Arabin cervical pessary, while other
studies did not specify the type of cervical pessary used; four studies
used McDonald cervical cerclage, two used McDonald or Shirodkar
cerclage, one used Lyubimova technique, one used Lyubimova or
Mammadaliyeva technique, while other studies did not mention the
specific technique used for cervical cerclage. The use of variable
pessary types or cerclage techniques may influence outcome data. 4) Few
studies reported all of these outcome measures and the quality of
included studies varied, which may affect the reliability of our
findings. 5) Few studies reported the potential complications (e.g.
vaginal drainage, infection, bleeding, intrauterine infection, neonatal
complications) or economic parameters (e.g. length of hospital stay,
cost) associated with cervical cerclage and cervical pessary. Only one
study reported the endpoint of mean gestational weeks extended. And
thus, it is not possible to analyze these outcomes in this study.
In conclusion, compared with transvaginal cervical cerclage, use of a
cervical pessary may decrease the risks of PPROM and premature birth
before 34 weeks. Given its advantages of easy-to-use and minimal damage,
cervical pessary may become a useful preventive intervention that
deserves widespread clinical application. However, due to the
limitations in the available evidence, more high-quality, large-scale,
multicenter studies are needed to further clarify its role in preterm
birth prevention.