Pessary Versus Cerclage With or Without Progesterone in Twins

This open label, multi-center, two-by-two factorial, randomised controlled trial aims to compare the effectiveness of cervical pessary to cervical cerclage and also to determine the effectiveness of vaginal progesterone for the prevention of PTB in women with a twin pregnancy and a cervix ≤28 mm.

All women with a twin pregnancy will undergo cervical length measurement and digital examination at screening. Prior to CL measurement, women will be given a short brochure outlining risk factors and available PTB prevention methods. Only women with a CL ≤28 mm will be eligible for the study. Eligible participants will be screened by midwives or gynaecologists, then participants will be provided a full participant Information Sheet, Consent Form and will be invited to a full discussion with investigators about the study. Eligible women will further undergo a speculum examination to assess the feasibility of treatment with either cerclage or cervical pessary with or without progesterone and to exclude premature rupture of the membranes (PROM), acute vaginitis and cervicitis. All eligible women will be invited to participate in the study.

After written informed consent, women will be randomly assigned in a 1:1:1:1 ratio to receive a cerclage, pessary, cerclage plus progesterone or pessary plus progesterone. Assignment to treatment allocation will be done via a web portal hosted by HOPE Research Center, Vietnam. The randomisation schedule will be computer-generated at HOPE Research Center, with a permuted random block size of 4 or 8. Blinding will not be possible due to the nature of interventions. However, neonatologists assessing the children will be unaware of treatment allocation. Apart from randomisation, patients will be followed up and treated according to local protocol.

Women allocated to a cervical cerclage will be receiving the intervention according to local protocol, within a week after randomisation. Briefly, 2 to 3 senior clinicians, who had experienced with cerclage, will perform cervical cerclage, using Mc Donald technique, under spinal anaesthesia with a single dose of prophylactic antibiotics.

For those who randomised to pessary group, a soft, flexible, silicone pessary, purchased from the manufacturer (Arabin®, Dr Arabin GmbH \& Co KG, Germany), will be inserted through the vagina, upward around the cervix by 4 senior clinicians, who had experienced with pessary used, within one week of randomisation. The size of the pessary will be determined at the time of speculum inspection (Arabin and Alfirevic, 2013).

In the cerclage plus progesterone group, 400 mg vaginal progesterone, purchased from the manufacturer (Cyclogest® 400mg, Actavis, United Kingdom), will be applied once daily at bedtime, within two days after cerclage insertion. Participants will be asked to record their drug application in a patient diary sheet for up to 140 days.

In the pessary plus progesterone group, 400 mg vaginal progesterone, purchased from the manufacturer (Cyclogest® 400mg, Actavis, United Kingdom), will be applied once daily at bedtime, within two days after pessary insertion, in addition to the pessary that has been placed. Participants will be asked to record their drug application in a patient diary sheet for up to 147 days.

In all groups, participants will be re-assessed at 14 days post-randomisation for any possible adverse event. After that, participants will be seen monthly or weekly per local protocol. CL measurement will not be performed routinely after randomisation, unless for patients' preference. In case the CL was shortened, further intervention, if any, will be based on the clinician's decision after a discussion with the patient.

In case of premature rupture of the membranes, active vaginal bleeding, other signs of preterm labor or severe patient discomfort, the vaginal progesterone and pessary or cerclage, will be removed. If participants develop (threatened) preterm labor, participants will receive treatment per local protocol. Intervention will be stopped at 37 0/7 weeks of gestation or at delivery.

Compliance rate to progesterone will be calculated by dividing the number of progesterone doses used since the last visit by the number of progesterone doses that should have been used since the last visit. Women will be defined as compliant when the compliance rate are over 80%.

Statistical analysis will be conducted according to the intention-to-treat principle, in which all randomised women will be considered in the primary comparison between treatment groups. The per-protocol analysis may be conducted, but these results would be considered exploratory only. All tests will be two-tailed, and differences with p-value <0.05 will be considered statistically significant.

In view of the two-by-two factorial design, the analysis will be done separately for cerclage versus pessary and for progesterone versus no progesterone. The investigators will test for interaction between CL and treatment effect on PTB <34 weeks and the composite of poor perinatal outcomes.

A pre-specified subgroup analysis in women with a CL <25th percentile, and at the 25-50th percentile, 50-75th percentile and >75th percentile is planned. The percentile will be determined based on the CL from all women after randomisation.

The investigators plan one interim analysis. The interim analysis will be performed by an independent statistician who will not directly involve in the study, after completion of data collection of the first 150 randomised patients. At interim analyses, data will be assessed for safety, efficacy, and futility. Safety will be assessed in terms of serious adverse events (perinatal death, maternal mortality or severe maternal morbidity). The interim analysis will be conducted using a two-sided significant test with the Haybittle-Peto spending function and a type I error rate of 5% with stopping criteria of p <0.001 (Z alpha = 3.29). Based on this report, the DSMB will provide guidance on whether to stop or continue the study.

A separated detailed statistical analysis plan will be developed and completed prior to data lock.

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices) and study protocol will be available, upon request from investigators whose proposed use of the data has been approved by an independent review committee ("learned intermediary") identified for this purpose to achieve aims in the approved proposal. Data will be available at the beginning 9 months and ending 36 months following article publication. Proposals should be directed to bsvinh.dq@myduchospital.vn. To gain access, data requestors will need to sign a data access agreement. Data are available for 5 years at https://www.project-redcap.org/.