IntroductionCervical insufficiency accounts for 15% of recurrent pregnancy losses between 16 and 28 weeks of gestation. The aim of the study is to verify the effectiveness of emergency double-level cerclage with vaginal progesterone in cervical insufficiency treatment in terms of the prevention of preterm delivery before 34 weeks of gestation.Methods and analysisThis trial is a multicentre, non-blinded, randomised study with 1:1 allocation ratio. The study is conducted at tertiary perinatal care departments in Poland. It will include patients with cervical insufficiency with the fetal membranes visible in the open cervical canal or protruding into the vagina between 16+0 and 23+6 weeks of pregnancy. They will be randomised into two arms: emergency single-level cerclage with vaginal progesterone or double-level cerclage with vaginal progesterone. All will be administered antibiotics and indomethacin. The primary outcome is the rate of deliveries below 34+0 weeks of gestation, while secondary outcomes include gestational age at delivery, neonatal outcomes, maternal outcomes according to the Core Outcome Set for Evaluation of Interventions to Prevent Preterm Birth and cerclage procedure complications. The planned number of participants according to the power analysis is 78.Ethics and disseminationThe study protocol was written in accordance with the Standard Protocol Items: Recommendations for Interventional Trials statement. It was created according to the requirements of the Declaration of Helsinki for Medical Research involving Human Subject. Ethical approval was obtained from the Ethics Committee of the Centre of Postgraduate Medical Education (no. 1/2022). The study protocol was approved and published by ClinicalTrials.gov (posted on 24 February 2022). All participants gave a written informed consent. After completion of the study its results will be published in a peer-reviewed English language journal.Trial registrationNCT05268640.

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