Predicting spontaneous preterm birth in asymptomatic high-risk women with cervical cerclage

Objective To determine the performance of the predictive markers of spontaneous preterm birth, cervicovaginal quantitative fetal fibronectin (fFN) and cervical length, in asymptomatic high-risk women with transabdominal, history-indicated or ultrasound-indicated cervical cerclage. Methods This was a secondary analysis of a prospective cohort of asymptomatic high-risk women with cervical cerclage and no other prophylactic intervention (including progesterone), who attended the preterm birth clinic at a central London teaching hospital between October 2010 and September 2016. Women had either transabdominal cerclage, placed prior to conception, history-indicated cerclage, placed before 14 weeks' gestation, or ultrasound-indicated cerclage for a short cervix (< 25 mm), placed before 24 weeks. All women underwent serial cervical length assessment on transvaginalultrasound in the second trimester (16- 28 weeks), and quantitative fFN testing from 18weeks onward. Test performance was analyzed for the prediction of spontaneous preterm birth before 30 weeks (cerclage failure), 34 weeks and 37weeks, using receiver-operating-characteristics (ROC)-curve analysis. Results Overall, 181 women were included in the analysis. Cervical length and fFN were strong predictors of spontaneous preterm birth before 30 weeks in women with cerclage, with areas under the ROC curve (AUC) of 0.86 (95% CI, 0.79- 0.94) and 0.84 (95% CI, 0.75- 0.92), respectively. Cervical length was a better predictor of preterm birth before 30 weeks in women with history-indicated compared to those with ultrasound-indicated cerclage, although both showed clinical utility (AUC, 0.96 (95% CI, 0.91- 1.00) vs 0.79 (95% CI, 0.66- 0.91); P= 0.01). Quantitative fFN was a strong predictor of spontaneous preterm birth before 30 weeks in women with history-indicated cerclage (AUC, 0.91 (95% CI, 0.75- 1.00)) and retained clinical utility in those with ultrasound-indicated cerclage (AUC, 0.76 (95% CI, 0.64- 0.89)). There were no spontaneous deliveries before 34weeks in women with a transabdominal cerclage, soAUCwas not calculated. Delivery was delayed significantly in this group ( P< 0.01). Conclusions Cervical length and quantitative fFN retain clinical utility for the prediction of spontaneous preterm birth in women with cervical cerclage, and prediction is best in women with a history-indicated stitch. These tests can be relied upon to discriminate risk and have utility when planning clinical management with regard to treatment failure. (c) 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.