Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery after multifetal pregnancy reduction

Abstract Objective The study was undertaken to assess the validity of vaginal fetal fibronectin assay as a screening test for spontaneous preterm delivery in asymptomatic patients who have undergone multifetal pregnancy reduction (MFPR). Study design A historic cohort of 63 patients who underwent MFPR between 10 and 14 weeks of gestation was identified. All patients underwent serial vaginal fetal fibronectin sampling every 2 to 3 weeks from 22 weeks of gestation until delivery or 32 weeks of gestation. The fetal fibronectin concentration was measured by enzyme-linked immunosorbent assay, with 50 ng/mL or greater indicating a positive result. Charts were reviewed for fetal fibronectin results and pregnancy outcome data. Groups were compared by use of Fisher exact test. Results There were 13 singleton and 50 twin gestations after MFPR. A median of 4 fetal fibronectin assays were performed per patient. A total of 234 fetal fibronectin assays were performed with 222 (94.9%) negative results and 12 (5.1%) positive results. Overall, 41.3% of gestations were delivered spontaneously before 37 weeks; 7.9% were delivered before 34 weeks. The mean interval between tests was 17.8 days (±7.2 days). For delivery within 2 and 3 weeks of a single test, fetal fibronectin had a sensitivity of 66.7% and 50%, a specificity of 95.7% and 96.1%, a positive predictive value of 16.7% and 25%, and a negative predictive value of 99.5% and 98.6%, respectively. Conclusion The fetal fibronectin test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies as in previously published cohorts.