Objective: We sought to evaluate whether the presence of a positive fetal fibronectin (> or = 50 ng/mL) in nulliparous women undergoing preinduction cervical ripening with the intracervical Foley catheter predicted vaginal birth.
Methods: This was a prospective blinded observational trial of nulliparous women undergoing preinduction cervical ripening. We excluded women who had a contraindication to vaginal birth. Cervical and vaginal fetal fibronectin specimens were obtained before preinduction cervical ripening with an intracervical Foley catheter. The managing obstetrician was blinded to these results.
Results: A total of 241 women met the inclusion criteria, of which 54.4% delivered vaginally. There was no difference in the rate of vaginal delivery among women with either a positive cervical fetal fibronectin (positive fetal fibronectin 55.8% compared with negative fetal fibronectin 53.3%, P = .70) or positive vaginal fetal fibronectin (positive fetal fibronectin 57.6% compared with negative fetal fibronectin 53.3%, P = .56). Women with a positive cervical fetal fibronectin did have a shorter duration of cervical ripening (fetal fibronectin-positive 229 +/- 220 minutes compared with fetal fibronectin-negative 379 +/- 193 minutes, P < .05), duration of oxytocin (fetal fibronectin-positive 655 +/- 555 minutes compared with fetal fibronectin-negative 731.5 +/- 342 minutes, P < .025) and required lower maximal doses of oxytocin (fetal fibronectin-positive 18.4 mIU/min compared with fetal fibronectin-negative 21.8 mIU/min, P = .005). Women with a positive vaginal fetal fibronectin demonstrated only a shorter duration of cervical ripening compared with their fetal fibronectin negative counterparts (fetal fibronectin-positive 300 +/- 216 minutes compared with fetal fibronectin-negative 345 +/- 201 minutes, P < .05).
Conclusion: Fetal fibronectin does not predict vaginal delivery in nulliparous women requiring preinduction cervical ripening.
Level of evidence: II-2.