Monofilament Suture Versus Braided Suture Thread to Improve Pregnancy Outcomes After Vaginal Cervical Cerclage (C-STICH): A Pragmatic Randomized, Controlled, Phase 3, Superiority Trial

Preterm birth complicates approximately 10% of pregnancies worldwide. It can lead to neonatal mortality or lifelong complications for those babies who survive. One cause of preterm birth is cervical insufficiency, which affects up to 1% of pregnant women and can be treated with the placement of vaginal cervical cerclage. There are 2 techniques for cervical cerclage: the modified Shirodkar cerclage, which involves dissecting the bladder and placing a suture around the supravaginal cervix with the suture thread buried, and the McDonald cerclage, which involves inserting the suture thread as high as possible around the upper section of the cervix. The effectiveness of either technique is dependent on perioperative decisions, such as suture thread choice. One UK survey found that 87% of clinicians prefer to use braided thread, with 13% preferring monofilament thread. The preference for braided thread was due to its easy handling and concerns that monofilament thread is difficult to remove if it becomes embedded in the cervix. However, an observational, nonrandomized systemic review suggested that monofilament thread was better than braided thread to prevent pregnancy loss (7% vs 18.9%; risk ratio [RR], 0.34; 95% confidence interval [CI], 0.18-0.63). Additional evidence suggests that monofilament thread is superior because braided thread could serve as a reservoir for bacteria, causing vaginal dysbiosis and increasing the risk of pregnancy loss. There are no randomized clinical trials to inform the choice of suture thread to prevent pregnancy loss. The aim of this study was to compare the effectiveness of monofilament suture thread to braided suture thread on pregnancy loss in women undergoing cervical cerclage. This was a superiority randomized clinical trial, conducted at 75 obstetric units in the United Kingdom between August 21, 2015, and January 28, 2021. Included were women aged 18 years and older with singleton pregnancies, who required vaginal cervical cerclage. Excluded were women who required emergency or rescue cerclage, needed immediate suture insertion, or had ruptured or visible membranes, as well as those who did not have a cerclage placed vaginally. Eligible women were randomized to receive either monofilament thread or braided thread. Women were followed up until 28 days postdelivery or hospital discharge, whichever came first. Preterm neonates were followed up until delivery or discharge, and babies born at term were followed up 28 days postdelivery or hospital discharge, whichever came first. A total of 2049 women were randomized to the monofilament suture thread group (n = 1025) or the braided suture thread group (1024). The intention-to-treat analysis included 1003 women in the monofilament group and 993 women in the braided group. No significant differences were observed in the rate of pregnancy loss between the monofilament group and braided group (8% vs 7.6%, respectively; RR, 1.05; 95% CI, 0.79-1.40; adjusted risk difference, 0.002; 95% CI, -0.02 to 0.03; P = 0.73). Insertion complications occurred in 4% of women in the monofilament group and 3% in the braided suture group. Women in the monofilament group experienced more removal complications than the braided group (RR, 1.25; 95% CI, 1.15-1.36). No significant differences were observed in maternal secondary outcomes or neonatal outcomes. In conclusion, there was no difference in the rate of pregnancy loss when using monofilament suture thread or braided suture thread in women undergoing cervical cerclage.