Support: (+84) 28 7308 5885 - (Ext) 303 or 310

Effectiveness of cervical pessary compared to cervical cerclage with or without vaginal progesterone for the prevention of preterm birth in women with twin pregnancies and a short cervix: study protocol for a two-by-two factorial randomised clinical trial

DOI: 10.1136/bmjopen-2019-036587

BMJ Open 10 (6): 1-7 – 2020-06-18

Vinh Q Dang1,2, Yen TN He2,3, Ha NH Pham1, Tuyen TT Trieu3, Trung Q Bui1, Nhu T Vuong1, Loc MT Nguyen2, Diem TN Nguyen2, Thanh V Le1, Wentao Li4, Cam H Le3, Ben W Mol4, Lan N Vuong5

Published: 13 May 2020

Author information


Women with twin pregnancies and a short cervix are at increased risk for preterm birth (PTB). Given the burden of prematurity and its attendant risks, the quest for effective interventions in twins has been an area of considerable research. Studies investigating the effectiveness of cervical cerclage, cervical pessary and vaginal progesterone in preventing PTB have yielded conflicting results. The aim of this study is to compare the effectiveness of cervical pessary and cervical cerclage with or without vaginal progesterone to prevent PTB in women with twin pregnancies and a cervical length (CL) ≤ 28 mm.
Methods and analysis
This multicentre, randomised clinical trial will be conducted at My Duc Hospital and My Duc Phu Nhuan Hospital, Vietnam. Asymptomatic women with twin pregnancies and a CL ≤28 mm, measured at 16–22 weeks’ gestation, will be randomised in a 1:1:1:1 ratio to receive a cerclage, pessary, cerclage plus progesterone or pessary plus progesterone. Primary outcome will be PTB <34 weeks. Secondary outcomes will be maternal and neonatal complications. We preplanned a subgroup analysis according to CL from all women after randomisation and divided into four quartiles. Analysis will be conducted on an intention-to treat basis. The rate of PTB <34 weeks’ gestation in women with twin pregnancies and a cervix ≤28 mm and treated with pessary in our previous study at My Duc Hospital was 24.2%. A sample size of 340 women will be required to show or refute that cervical cerclage decreases the rate of PTB <34 weeks by 50% compared with pessary (from 24.2% to 12.1%, α level 0.05, power 80%, 5% lost to follow-up and protocol deviation). This study is not to be powered to assess interactions between interventions.
Ethics and dissemination
Ethical approval was obtained from the Institutional Ethics Committee of My Duc Hospital and informed patient consent was obtained before study enrolment. Results of the study will be submitted for publication in a peer-reviewed journal.
Strengths and limitations of this study
– The trial has a randomised, controlled design, which should minimise bias.
– A limited number of well-trained, certified staffs will be involved in cervical length measurement, pessary and cerclage placement which increases the validity of the study.
– An open design, which is unavoidable due to the nature of the interventions, could introduce bias.
– The majority of women with twin pregnancies involving in the trial will conceive from assisted reproductive technology. Therefore, the external validity of the study might be compromised.
Trial registration number NCT03863613 (date of registration: 4 March 2019).