Prediction of spontaneous preterm birth in patients with congenital uterine anomalies using combined fetal fibronectin and cervical length

Objective: To evaluate cervical length (CL) and fetal fibronectin (fFN) as predictors of spontaneous preterm birth (SPTB) in patients with congenital uterine anomalies. Methods: A retrospective cohort of patients with uterine anomalies and singleton pregnancies >22 weeks delivered by one maternal fetal medicine practice from 2005-2012 who underwent routine CL and fFN testing from 22-32 weeks was identified. We excluded patients with a cerclage, and patients who had an indicated preterm birth <37 weeks. A short CL was defined as ≤25 mm. We compared rates of spontaneous preterm birth <37 weeks based on CL and fFN results. Results: 120 patients with uterine anomalies were identified (47 septate, 36 bicornuate, 12 unicornuate, 10 arcuate, 9 T-shaped, 6 didelphys). Seventeen (14.2%) of patients had a short CL; these patients had a higher incidence of spontaneous preterm birth <37 weeks (64.7% vs. 13.6%, p<0.001). Six of 89 patients (6.7%) had a positive fFN; these patients did not have an increased incidence of spontaneous preterm birth than patients with a negative fFN. The addition of fFN to CL testing did not improve the positive or negative predictive values, nor the positive or negative likelihood ratios for spontaneous preterm birth <37 weeks. Conclusions: In women with uterine anomalies, a short CL is significantly associated with spontaneous preterm birth <37 weeks. The addition of fFN testing in these patients does not improve the prediction of preterm birth.