Although cerclage pessary was proposed as a treatment option for cervical incompetence as early as 1959, 1 there are only limited data from small observational case series on its effectiveness in reducing preterm birth in high-risk groups of patients. 2-8 The majority of these studies have used the Arabin pessary, which is a flexible, ringlike silicone pessary that is available in various sizes. Dharan and Ludmir summarized those case series and reported that among 121 women with prior history

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... f preterm birth or high-risk factors, 63% achieved a term delivery in their subsequent pregnancy when treated with the pessary. 9 The pessary is thought to act by changing the inclination of the cervical canal, 2 and it may be a safer alternative to surgical cerclage. 9 However, evidence to support the use of cervical pessary from randomized controlled studies is limited. In 2010, the Cochrane Library performed a systematic review to evaluate the efficacy of cerclage pessary for prevention of preterm birth. Two randomized trials 10,11 were found, but both were Keywords ► cerclage pessary ► short cervix ► preterm birth Abstract Objective To determine the effectiveness of cerclage pessary in the prevention of preterm birth in asymptomatic Chinese women with a short cervix at 20 to 24 weeks. Methods Low-risk women carrying singleton pregnancies were screened with transvaginal ultrasound, and those with a cervical length <25 mm at 20 to 24 weeks were recruited into a randomized controlled trial, comparing the prophylactic use of cerclage pessary with expectant management. The analysis was by intent-to-treat. The primary outcome measure was preterm delivery before 34 weeks. Results Among 4438 screened women, 203 women (4.6%) met the inclusion criteria and 108 (58%) consented for the study. A total of 53 and 55 women were allocated to pessary and control groups, respectively. There was no difference in background demographics, including the mean cervical length (19.6 mm versus 20.5 mm) and the mean gestational age at randomization (both 21.9 weeks). Delivery before 34 weeks occurred in 9.4% and 5.5% (p ¼ 0.46) in the pessary and the control groups, respectively. No differences in major side effects were noted between the groups. Conclusion In our population, <5% had a cervical length of less than 25 mm at 20 to 24 weeks' gestation. The prophylactic use of cerclage pessary did not reduce the rate of preterm delivery before 34 weeks.