Cervical stitch for preventing preterm birth in women with a multiple pregnancy

Background
Carrying more than one baby increases a woman's risk of delivering preterm. The risks increase with the number of babies being carried. Babies born prematurely are more likely to experience poor outcomes including serious ill health and death. Cervical cerclage is a surgical procedure carried out during pregnancy to try to prevent preterm birth by limiting shortening and opening of the cervix. It is performed by placing suture material around the cervix, which is accessed either by the vagina or through the mother’s abdomen. The effectiveness and safety of this procedure for multiple gestations remains uncertain. The likelihood of spontaneous preterm birth can be assessed by looking at the mother’s obstetric history, a physical examination, or transvaginal ultrasound examination in the second trimester.

Review question
To assess whether the use of a cervical stitch in women with multiple gestations at high risk of pregnancy loss improves obstetrical and perinatal outcomes.

Study Characteristics
We included five trials, which involved a total of 1577 women, comparing cerclage with no cerclage in women with either singleton and multiple gestations. After excluding singletons, our final analysis included 128 women, of which 122 were pregnant with twins, and six were pregnant with triplets. Cerclage was indicated by obstetric history in two trials (n = 73 women) and transvaginal ultrasound in three trials (n = 55 women).

Main findings
When cerclage was compared with no cerclage in women with multiple gestations, there was no difference in perinatal deaths or neonatal ill health, or preterm birth rates. However, the number of women included in the five studies was insufficient to provide meaningful conclusions.

The long-term effect of cerclage on neurodevelopmental outcomes in the surviving infants and maternal infection and side- effects could not be estimated. It was therefore unclear if cerclage for women with multiple pregnancies puts the health of either the mothers or the infants at risk in any way.

Quality of the evidence
The five included studies were generally considered to be of average to above average quality, but three of the studies were difficult to assess fully because of missing methodological information.

We did not find any studies comparing different indications for cerclage (obstetric history-indicated versus ultrasound-indicated cerclage) or comparing cerclage to another intervention (such as progesterone).

Authors' conclusions: 

This review is based on limited data from five small studies of average to above average quality. For multiple gestations, there is no evidence that cerclage is an effective intervention for preventing preterm births and reducing perinatal deaths or neonatal morbidity.

Read the full abstract...
Background: 

Cervical cerclage is a surgical intervention involving placing a stitch around the uterine cervix. The suture material aims to prevent cervical shortening and opening, thereby reducing the risk of preterm birth. The effectiveness and safety of this procedure in multiple gestations remains controversial.

Objectives: 

To assess whether the use of a cervical cerclage in multiple gestations, either at high risk of pregnancy loss based on just the multiple gestation (history-indicated cerclage), the ultrasound findings of 'short cervix' (ultrasound-indicated cerclage), or the physical exam changes in the cervix (physical exam-indicated cerclage), improves obstetrical and perinatal outcomes. The primary outcomes assessed were perinatal deaths, serious neonatal morbidity, and perinatal deaths and serious neonatal morbidity.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2014) and reference lists of retrieved studies.

Selection criteria: 

All randomised controlled trials (RCTs) of cervical cerclage in multiple pregnancies. Quasi-RCTs and RCTs using a cluster-randomised design were eligible for inclusion (but none were identified). Studies using a cross-over design and those presented only as abstracts were not eligible for inclusion.

We included studies comparing cervical cerclage with no cervical cerclage in multiple pregnancies.

Studies comparing cervical stitch versus any other preventative therapy (e.g. progesterone) in multiple pregnancies, and studies involving comparisons between different cerclage protocols (history-indicated versus ultrasound-indicated versus physical exam-indicated cerclage) were also eligible for inclusion but none were identified.

Data collection and analysis: 

Two review authors independently assessed trials for inclusion and risk of bias. Two review authors extracted data. Data were checked for accuracy.

Main results: 

We included five trials, which in total randomised 1577 women, encompassing both singleton and multiple gestations. After excluding singletons, the final analysis included 128 women, of which 122 women had twin gestations, and six women had triplet gestations. Two trials (n = 73 women) assessed history-indicated cerclage, while three trials (n = 55 women) assessed ultrasound-indicated cerclage. The five trials were judged to be of average to above average quality, with three of the trials at unclear risk regarding selection and detection biases.

Concerning the primary outcomes, when outcomes for cerclage were pooled together for all indications and compared with no cerclage, there was no statistically significant differences in perinatal deaths (19.2% versus 9.5%; risk ratio (RR) 1.74, 95% confidence intervals (CI) 0.92 to 3.28, five trials, n = 262), serious neonatal morbidity (15.8% versus 13.6%; average RR 0.96, 95% CI 0.13 to 7.10, three trials, n = 116), or composite perinatal death and neonatal morbidity (40.4% versus 20.3%; average RR 1.54, 95% CI 0.58 to 4.11, three trials, n = 116).

Among the secondary outcomes, there were no significant differences between the cerclage and the no cerclage groups. To name a few, there were no significant differences among the following: preterm birth less than 34 weeks (average RR 1.16, 95% CI 0.44 to 3.06, four trials, n = 83), preterm birth less than 35 weeks (average RR 1.11, 95% CI 0.58 to 2.14, four trials, n = 83), low birthweight less than 2500 g (average RR 1.10, 95% CI 0.82 to 1.48, four trials, n = 172), very low birthweight less than 1500 g (average RR 1.42, 95% CI 0.52 to 3.85, four trials, n = 172), and respiratory distress syndrome (average RR 1.70, 95% CI 0.15 to 18.77, three trials, n = 116). There were also no significant differences between the cerclage and no cerclage groups when examining caesarean section (elective and emergency) (RR 1.24, 95% CI 0.65 to 2.35, three trials, n = 77) and maternal side-effects (RR 3.92, 95% CI 0.17 to 88.67, one trial, n = 28).

Examining the differences between prespecified subgroups, ultrasound-indicated cerclage was associated with an increased risk of low birthweight (average RR 1.39, 95% CI 1.06 to 1.83, Tau² = 0.01, I² = 15%, three trials, n = 98), very low birthweight (average RR 3.31, 95% CI 1.58 to 6.91, Tau² = 0, I² = 0%, three trials, n = 98), and respiratory distress syndrome (average RR 5.07, 95% CI 1.75 to 14.70, Tau² = 0, I² = 0%, three trials, n = 98). However, given the low number of trials, as well as substantial heterogeneity and subgroup differences, these data must be interpreted cautiously.

No trials reported on long-term infant neurodevelopmental outcomes. There were no physical exam-indicated cerclages available for comparison among the studies included.

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