Predicting spontaneous preterm birth with cervical length and fetal fibronectin for symptomatic women of threatened preterm labor: A prospective study

Abstract

Introduction: The aim of this study was to assess the effectiveness of fetal fibronectin (fFN) in combination with cervical length for predicting spontaneous preterm birth (sPTB) in women presenting with threatened preterm labor. Material and Methods: This was a prospective study involving singleton pregnancies at 20–36 weeks of gestation with symptoms of threatened preterm labor. Upon admission, cervical length (CL) and fFN test in cervicovaginal secretions were measured. Logistic regression analysis was performed to develop the following models: CL alone, fFN at various thresholds, and their combined models for the prediction of sPTB. Area under the receiver operating characteristic curve (AUROC) was calculated. Results: A total of 398 cases were analyzed. The median gestational age at recruitment was 30.1 weeks. Among these cases, 55 (13.8%) cases had sPTB at <37 weeks of gestation. A history of preterm birth (HxPTB), shorter CL, and increased fFN level were independently associated with an increased risk of sPTB. AUROC of the fFN test, at ≥50 ng/mL or ≥200 ng/mL, was significantly higher than that of ≥500 ng/mL for predicting sPTB. For the prediction of sPTB, the AUROCs were 0.78 for CL, 0.78 for fFN, and 0.84 for the combination of HxPTB, CL, and fFN ≥50 ng/mL. The ROC curves showed that, at a false-positive rate of 10%, the sensitivities were 53% for CL ≤2.44 cm, 33.9% for fFN ≥50 ng/mL, and 60% for the combination of HxPTB, CL, and fFN ≥50 ng/mL (p < 0.05). Conclusions: In women symptomatic of threatened preterm labor, a combination of fFN and CL has improved the predictive performance of sPTB compared with either measure alone.