Ultrasound-indicated cervical cerclage: Outcome depends on preoperative cervical length and presence of visible membranes at time of cerclage

Objective: The purpose of this study was to assess cases of ultrasound-indicated cervical cerclage and to relate preoperative cervical length, operative findings, postoperative cervical length, and pregnancy outcome to establish the appropriate criteria to offer cervical cerclage. Study Design: A prospective observational study comprised 380 women at high risk of preterm labor who underwent serial transvaginal ultrasonographic assessment of cervical length. Seventy-three women had criteria for and underwent cervical cerclage. Data concerning preoperative cervical length, operative findings, postoperative cervical length, and pregnancy outcome were collected. Statistical analysis was performed with Mann-Whitney and Fisher exact tests. Results: There was a significant increase in median cervical length after cerclage, 15.0 versus 25.0 mm (P< .0001). Preoperative cervical length and postoperative upper cervical length were independently better predictors of outcome than postoperative entire cervical length. Fetal membranes were visible in 18% of cases at the time of suture insertion, which was associated with a significantly worse outcome, regardless of preoperative cervical length. Of those 41 women with a very short preoperative cervical length (≤15 mm), outcome was significantly worse in those women with visible fetal membranes at the time of cerclage compared with those women with no visible fetal membranes at the time of cerclage: median gestational age at delivery, 23 weeks versus 37 weeks 4 days (P = .002); suture insertion to delivery interval, 19 days versus 108 days (P = .0004); and fetal survival rates, 50% versus 86% (P = .03). Conclusion: In a high-risk population that undergoes serial transvaginal ultrasound surveillance of cervical length, the presence of visible fetal membranes at the time of suture insertion, regardless of preoperative cervical length, is associated with a poor outcome. Fetal membranes were not visible in any cases with a preoperative cervical length of >15 mm. These findings lend support to a practice of offering cerclage at or above a cervical length of 15 mm. (Am J Obstet Gynecol 2002;187:445-9.)