The predictive value of sequential cervical length screening in singleton pregnancies after cerclage: a retrospective cohort study

BACKGROUND: There are few valid predictors for preterm delivery after cerclage. Experience with a screening program that included four sequential cervical length measurements in singleton pregnancies after cerclage is reviewed. METHODS: In this retrospective cohort study, 88 singleton pregnancies after cerclage were included. Cervical length (CL) measurements were performed perioperatively and at weeks 16 + 0, 18 + 0, 20 + 0, and 22 + 0 by transvaginal ultrasound. Predictive factors for early preterm delivery included patient characteristics, obstetric history and CL measurements and were analyzed separately for women with ultrasound-indicated cerclage and those with history-indicated cerclage. Women with emergency cerclage were excluded. RESULTS: In women with delivery <35 weeks, CL declined from the 16 + 0 to the 22 + 0 weeks of gestation (p = 0.009). In univariate analysis, all CL measurements were predictive for delivery <35 weeks in women who underwent ultrasound-indicated cerclage and in women who received a history-indicated cerclage, whereas in multivariate analysis only CL three to six days after cerclage remained significant (odds ratio 0.85, 95 % CI 0.73–0.98). In women with ultrasound-indicated cerclage, optimized cut-off was ≤20 mm (specificity 83.8 %, sensitivity 84.2 %). CONCLUSIONS: CL measured three to six days after cerclage placement provides the best information about the risk for delivery <35 weeks.