Evaluation of Salivary Estriol Dynamics and Cervicovaginal Oncofetal Fibronectin for the Prediction of Impending Preterm Labor

International Journal of Obstetrics and Gynecology | Vol. 14, No. 8, August 2026 | pp. 531–542

DOI: 10.46882/2026/IJOG/000525

Original Research Article

Title: Evaluation of Salivary Estriol Dynamics and Cervicovaginal Oncofetal Fibronectin for the Prediction of Impending Preterm Labor

Names of Authors: Oluwaseun A. Adebayo¹, Chinedu O. Okafor², Aminat Z. Yusuf¹

Authors’ Affiliations:
¹ Department of Obstetrics and Gynecology, College of Medicine, University of Lagos, Lagos, Nigeria
² Department of Maternal-Fetal Medicine, University of Nigeria Teaching Hospital, Enugu, Nigeria

Abstract:
Early identification of true preterm labor among symptomatic women remains vital to avoid unnecessary hospitalizations and target prophylactic glucocorticoid therapy. This prospective multi-center diagnostic accuracy study evaluated the predictive value of combining longitudinal salivary estriol monitoring with a point-of-care cervicovaginal fetal fibronectin (fFN) test in women presenting with threatened preterm labor. A cohort of 180 symptomatic singleton pregnancies between 24 and 34 weeks of gestation was enrolled. Salivary samples were analyzed using enzyme immunoassay, and a positive fFN threshold was set at ≥ 50 ng/mL. The primary clinical outcome was spontaneous delivery within 7 days of initial presentation. True preterm delivery within 7 days occurred in 22 participants (12.2%). Salivary estriol levels above a baseline threshold of 2.1 ng/mL coupled with a positive fFN test demonstrated an exceptional diagnostic performance, yielding a sensitivity of 90.9%, a specificity of 94.3%, a positive predictive value of 69.0%, and a negative predictive value of 98.7%. The Area Under the Curve (AUC) for the combined biomarkers was 0.95, significantly outperforming individual fFN testing (AUC = 0.81, p = 0.006) or standalone digital cervical assessment. In conclusion, integrating salivary estriol dynamics with cervicovaginal fetal fibronectin metrics provides a highly reliable, non-invasive diagnostic framework to predict imminent preterm delivery within a 7-day window, optimizing maternal transport and therapeutic triage.

Keywords: Preterm Labor; Fetal Fibronectin; Salivary Estriol; Diagnostic Accuracy; Premature Birth; Biomarkers.

Manuscript Timeline: Received: June 08, 2026; Revised: July 25, 2026; Accepted: August 06, 2026; Published: August 30, 2026.

Citation: Adebayo OA, Okafor CO, Yusuf AZ. Evaluation of Salivary Estriol Dynamics and Cervicovaginal Oncofetal Fibronectin for the Prediction of Impending Preterm Labor. International Journal of Obstetrics and Gynecology. 2026; 14(8): 531–542.

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