Cervical Occlusion Two-level Stitch Application (COSA)

  • End date
    Feb 28, 2025
  • participants needed
  • sponsor
    Centre of Postgraduate Medical Education
Updated on 1 May 2022


Cervical insufficiency is defined as painless dilatation of the cervix during the second trimester of pregnancy. As a result of shortening and opening of the cervix, despite the lack of uterine contractions, the fetal membranes invade into the cervical canal and then into the vagina, which results in premature rupture of the membranes and miscarriage or preterm delivery. Cervical insufficiency occurs in approximately 1% of the women. The aim of the study is to evaluate the effectiveness of placing a two-level cervical cerclage in the treatment of advanced cervical insufficiency. The hypothesis assumes that the insertion of a two-level suture is associated with a reduction in the rate of deliveries < 34 weeks of gestation in comparison to single-level suture. The study will include women with fetal membranes visible through open external os of the cervix between 16+0 and 23+6 weeks. They will be randomized to two arms - McDonald's single cervical cerclage or two-level cerclage.


This is an open-label, multicentre, prospective, randomised controlled trial (RCT). Women will be randomized to the single-level cerclage arm or the double-level cerclage. Each patient will have a vaginal swab for aerobic and anaerobic bacteria and fungi culture, as well as for mycoplasmas, chlamydia and ureaplasma performed. Each patient will be treated with progesterone (vaginally 2 x 100 mg per day) and empirical antibiotic therapy (ceftriaxone 2.0 g iv + clarithromycin 2 x 500 mg po + metronidazole 3 x 500 mg iv for 7 days). If specific pathogens will be detected, the antibiotic therapy will be modified according to the antibiogram. If the diagnosis of cervical insufficiency will be made >23 weeks of gestation a single course of corticosteroid therapy will be administered (betamethasone 2 x 12 mg im). Indomethacin will also be administered for 48 hours (starting the day of cerclage administration, indomethacin 2 x 75 mg po for 48 hours). In the ingle-level cerclage arm McDonald suture will be administered. In the double-level cerclage arm two separate sutures analogous to McDonald technique will be placed, one approximately 1 cm higher above the other. Patients will be followed up until miscarriage or delivery and will receive standard perinatal care. Gestational age at delivery, the occurrence of cerclage complications and neonatal outcomes will be analyzed.

Condition Cervical Incompetence
Treatment Double-level cervical cerclage, Single-level cervical cerclage
Clinical Study IdentifierNCT05268640
SponsorCentre of Postgraduate Medical Education
Last Modified on1 May 2022


Yes No Not Sure

Inclusion Criteria

singleton pregnancy
gestational age 16+0 to 23+6 weeks
live fetus
cervical incompetence with fetal membranes visible through external os before 24+0 weeks of gestation

Exclusion Criteria

preterm rupture of membranes
vaginal bleeding
regular uterine contractions
maternal fever
diagnosed fetal genetic disorders
diagnosed major fetal anomalies
multiple pregnancy
congenital uterine anomalies
fetal demise
maternal leukocyte count >20 million/microliter
maternal serum C-reactive protein concentration > 20 mg/L
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