BACKGROUND The optimal approach to prevent preterm birth (PTB) in twins has not been fully established yet. Recent evidence suggests that placement of cervical cerclage in twin pregnancies with short cervical length at ultrasound or cervical dilatation at physical examination might be associated with a reduced risk of PTB. However, such evidence is based mainly on small studies thus questioning the robustness of these findings. The aim of this systematic review was to determine the role of cervical cerclage in preventing PTB and adverse maternal or perinatal outcomes in twin pregnancies. METHODS AND FINDINGS Key databases searched and date of last search: MEDLINE, Embase, and CINAHL were searched electronically on 20 April 2023. Eligibility criteria: Inclusion criteria were observational studies assessing the risk of PTB among twin pregnancies undergoing cerclage versus no cerclage and randomized trials in which twin pregnancies were allocated to cerclage for the prevention of PTB or to a control group (e.g., placebo or treatment as usual). The primary outcome was PTB <34 weeks of gestation. The secondary outcomes were PTB <37, 32, 28, 24 weeks of gestation, gestational age at birth, the interval between diagnosis and birth, preterm prelabor rupture of the membranes (pPROM), chorioamnionitis, perinatal loss, and perinatal morbidity. Subgroup analyses according to the indication for cerclage (short cervical length or cervical dilatation) were also performed. Risk of bias assessment: The risk of bias of the included randomized controlled trials (RCTs) was assessed using the Revised Cochrane risk-of-bias tool for randomized trials, while that of the observational studies using the Newcastle-Ottawa scale (NOS). Statistical analysis: Summary risk ratios (RRs) of the likelihood of detecting each categorical outcome in exposed versus unexposed women, and (b) summary mean differences (MDs) between exposed and unexposed women (for each continuous outcome), with their 95% confidence intervals (CIs) were computed using head-to-head meta-analyses. Synthesis of the results: Eighteen studies (1,465 twin pregnancies) were included. Placement of cervical cerclage in women with a twin pregnancy with a short cervix at ultrasound or cervical dilatation at physical examination was associated with a reduced risk of PTB <34 weeks of gestation (RR: 0.73, 95% CI [0.59, 0.91], p = 0.005 corresponding to a 16% difference in the absolute risk, AR), <32 (RR: 0.69, 95% CI [0.57, 0.84], p < 0.001; AR: 16.92%), <28 (RR: 0.54, 95% [CI 0.43, 0.67], 0.001; AR: 18.29%), and <24 (RR: 0.48, 95% CI [0.23, 0.97], p = 0.04; AR: 15.57%) weeks of gestation and a prolonged gestational age at birth (MD: 2.32 weeks, 95% [CI 0.99, 3.66], p < 0.001). Cerclage in twin pregnancy with short cervical length or cervical dilatation was also associated with a reduced risk of perinatal loss (RR: 0.38, 95% CI [0.25, 0.60], p < 0.001; AR: 19.62%) and composite adverse outcome (RR: 0.69, 95% CI [0.53, 0.90], p = 0.007; AR: 11.75%). Cervical cerclage was associated with a reduced risk of PTB <34 weeks both in women with cervical length <15 mm (RR: 0.74, 95% CI [0.58, 0.95], p = 0.02; AR: 29.17%) and in those with cervical dilatation (RR: 0.68, 95% CI [0.57, 0.80], p < 0.001; AR: 35.02%). The association between cerclage and prevention of PTB and adverse perinatal outcomes was exclusively due to the inclusion of observational studies. The quality of retrieved evidence at GRADE assessment was low. CONCLUSIONS Emergency cerclage for cervical dilation or short cervical length <15 mm may be potentially associated with a reduction in PTB and improved perinatal outcomes. However, these findings are mainly based upon observational studies and require confirmation in large and adequately powered RCTs.

中文翻译：

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宫颈环扎术预防宫颈长度短或宫颈扩张的双胎妊娠中的早产和不良围产期结局：系统评价和荟萃分析。

背景 预防双胞胎早产（PTB）的最佳方法尚未完全确定。最近的证据表明，在超声检查中宫颈长度较短的双胎妊娠中进行宫颈环扎术或在体检时进行宫颈扩张可能与降低 PTB 风险相关。然而，这些证据主要基于小型研究，因此质疑这些发现的稳健性。本系统评价的目的是确定宫颈环扎术在预防双胎妊娠中的 PTB 和不良孕产妇或围产期结局中的作用。方法和结果 检索的关键数据库和上次检索日期：2023 年 4 月 20 日以电子方式检索了 MEDLINE、Embase 和 CINAHL。 纳入标准：纳入标准是评估接受环扎术与不接受环扎术的双胎妊娠中发生 PTB 风险的观察性研究和随机试验其中双胎妊娠被分配至环扎组以预防 PTB 或分配至对照组（例如安慰剂或照常治疗）。主要结局是妊娠 34 周以下的 PTB。次要结局是 PTB < 37、32、28、24 孕周、出生时孕龄、诊断与出生之间的时间间隔、早产前胎膜破裂 (pPROM)、绒毛膜羊膜炎、围产儿流失和围产期发病率。还根据环扎指征（宫颈长度短或宫颈扩张）进行了亚组分析。偏倚风险评估：使用修订的 Cochrane 随机试验偏倚风险工具评估纳入的随机对照试验 (RCT) 的偏倚风险，而使用纽卡斯尔-渥太华量表 (NOS) 评估观察性研究的偏倚风险。统计分析：检测暴露与未暴露女性中每个分类结果的可能性的汇总风险比 (RR)，以及 (b) 暴露与未暴露女性之间（针对每个连续结果）的汇总平均差异 (MD)，其置信度为 95%使用头对头荟萃分析计算间隔（CI）。结果综合：纳入 18 项研究（1,465 例双胎妊娠）。对于超声检查时宫颈较短或体检时宫颈扩张的双胎妊娠妇女进行宫颈环扎术可降低妊娠 34 周以下的 PTB 风险（RR：0.73，95% CI [0.59，0.91]，p = 0.005 对应于绝对风险差异 16%，AR），<32（RR：0.69，95% CI [0.57，0.84]，p < 0.001；AR：16.92%），<28（RR：0.54，95） % [CI 0.43, 0.67], 0.001; AR: 18.29%) 和 <24 (RR: 0.48, 95% CI [0.23, 0.97], p = 0.04; AR: 15.57%) 孕周和孕龄延长出生时（MD：2.32 周，95% [CI 0.99, 3.66]，p < 0.001）。宫颈长度短或宫颈扩张的双胎妊娠中的环扎术也与围产期流产风险降低相关（RR：0.38，95% CI [0.25，0.60]，p < 0.001；AR：19。62%）和复合不良结果（RR：0.69，95% CI [0.53，0.90]，p = 0.007；AR：11.75%）。宫颈环扎术与宫颈长度<15毫米的女性（RR：0.74，95％CI [0.58，0.95]，p = 0.02；AR：29.17％）和宫颈长度<34周的女性相比，PTB风险降低相关。扩张（RR：0.68，95% CI [0.57，0.80]，p < 0.001；AR：35.02%）。环扎术和预防 PTB 与不良围产期结局之间的关联完全是由于纳入了观察性研究。GRADE 评估中检索到的证据质量较低。结论 宫颈扩张或宫颈长度短<15 mm 的紧急环扎术可能与减少 PTB 和改善围产期结局相关。然而，这些发现主要基于观察性研究，需要在大型且充分的随机对照试验中得到证实。