Fetal fibronectin, cervical length, and the risk of preterm birth in patients with an ultrasound or physical exam indicated cervical cerclage

Objective: To estimate the risk of preterm birth in patients with an ultrasound or physical exam indicated cervical cerclage based on the results of fetal fibronectin (fFN) and cervical length (CL) screening.;Methods: Retrospective cohort of patients with a singleton pregnancy and an ultrasound or physical exam indicated Shirodkar cerclage placed by one maternal-fetal medicine practice from November 2005 -- January 2015. Patients routinely underwent serial CL and fFN testing from 22-32 weeks. Based on ROC curve analysis, a short CL was defined as ≤15mm. All fFN and CL results included are from after the cerclage placement.;Results: 104 patients were included. Seventy eight (75%) patients had an ultrasound-indicated cerclage and 26 (25%) patients had a physical exam-indicated cerclage. A positive fFN was associate with preterm birth <32 weeks (15.6% vs. 4.2%, p=0.043), <35 weeks (37.5% vs. 11.1%, p=0.002), <37 weeks (65.6% vs. 20.8%, p<0.001), and earlier gestational ages at delivery (35.2+/-3.9 vs. 37.4+/-2.9, p=0.001). A short CL was also associated with preterm birth <35 weeks (50.0% vs. 11.9%, p<0.01), preterm birth <37 weeks (55.0% vs. 29.8%, p=0.033), and earlier gestational ages at delivery (34.8+/-4.1 vs. 37.2+/-3.0, p=0.004). The risk of preterm birth <32, <35, and <37 weeks increased significantly with the number of abnormal markers.;Conclusion: In patients with an ultrasound or physical exam indicated cerclage, a positive fFN and a short CL are both associated with preterm birth. The risk of preterm birth increases with the number of abnormal biomarkers.