Cervical cerclage prevents preterm birth in twin pregnancies

Twin pregnancies that undergo emergency cerclage for short cervix at ultrasound or cervical dilatation at physical examination are at lower risk of preterm birth (PTB) and have better perinatal outcomes than those not undergoing such intervention, results of a systematic review and meta-analysis have shown.

“However, these findings are mainly based upon observational studies and require confirmation in large and adequately powered randomized controlled trials (RCTs),” the investigators said.

The databases of Medline, Embase, and Cinahl were searched for observational studies assessing PTB risk among twin pregnancies undergoing cerclage relative to no cerclage and randomized trials in which twin pregnancies were allocated to cerclage for the prevention of PTB or to a control group (eg, placebo or treatment as usual).

The investigators assessed the risk of bias in RCTs using the Revised Cochrane risk-of-bias tool and in observational studies using the Newcastle‒Ottawa scale (NOS). They used head-to-head meta-analyses to compute summary risk ratios (RRs) and summary mean differences (MDs) between exposed and unexposed women (for each continuous outcome).

Eighteen studies, including 1,465 twin pregnancies, met the eligibility criteria. Women with a twin pregnancy who underwent cervical cerclage were less likely to experience preterm birth <34 weeks of gestation (RR, 0.73, 95 percent confidence interval [CI], 0.59‒0.91; p=0.005; absolute risk [AR], 16 percent), <32 weeks (RR, 0.69, 95 percent CI, 0.57‒0.84; p<0.001; AR, 16.92 percent), <28 weeks (RR, 0.54, 95 percent CI, 0.43‒0.67; p=0.001; AR, 18.29 percent), and <24 weeks (RR, 0.48, 95 percent CI, 0.23‒0.97; p=0.04; AR, 15.57 percent) and have a prolonged gestational age at birth (MD, 2.32 weeks, 95 percent CI, 0.99‒3.66; p<0.001). [PLoS Med 2023;20:e1004266]

Adverse outcome

Cerclage in pregnancies with short cervix or cervical dilatation also contributed to a lower risk of perinatal loss (RR, 0.38, 95 percent CI, 0.25‒0.60; p<0.001; AR, 19.62 percent) and composite adverse outcome (RR, 0.69, 95 percent CI, 0.53‒0.90; p=0.007; AR, 11.75 percent). In addition, cervical cerclage resulted in a reduced risk of PTB <34 weeks both in women with cervical length <15 mm (RR, 0.74, 95 percent CI, 0.58‒0.95; p=0.02; AR, 29.17 percent) and in those with cervical dilatation (RR, 0.68, 95 percent CI, 0.57‒0.808; p<0.001; AR, 35.02 percent).

Notably, the inclusion of observational studies facilitated the association between cerclage and prevention of PTB and adverse perinatal outcomes. At GRADE assessment, the quality of retrieved evidence turned out to be low.

“In the current review, we have also confirmed the potential beneficial role of cerclage in reducing the risk of PTB and neonatal morbidity in twin pregnancies with a cervical length <15 mm, similar to that reported in singleton pregnancies,” the investigators said.

“Conversely, in women with a cervical length of 15 to 25 mm, cerclage was not associated with a reduction in the risk of any of the outcomes assessed,” they added.

These findings supported those of studies on the predictive accuracy of ultrasound in twin pregnancies, which reported that lower cutoffs of cervical length compared to those used in singletons better in PTB in multiple gestations. [BJOG 2016;123:877-884]

“The findings from the present systematic review highlight the need for designing an appropriately powered RCT to elucidate whether the placement of a cervical cerclage may prevent PTB in women presenting with short cervical length at ultrasound assessment or cervical dilatation at physical examination,” the investigators said.