The prediction of recurrent preterm birth in patients on 17-alpha-hydroxyprogesterone caproate using serial fetal fibronectin and cervical length

Objective The objective of the study was to estimate the predictive value of cervical length (CL) and fetal fibronectin (fFN) in patients being treated with 17-alpha-hydroxyprogesterone caproate (17P). Methods This was a retrospective cohort of 176 patients with a prior spontaneous preterm birth being treated with weekly injections of 17P who underwent serial CL and fFN screening. Results A short CL (≤25 mm) was significantly associated with an earlier gestational age at delivery and with recurrent preterm birth at less than 37, less than 35, less than 34, and less than 32 weeks. A positive fFN was not significantly associated with recurrent preterm birth. As a screening test for recurrent preterm birth, the positive and negative likelihood ratios for CL were 2.04 and 0.35, respectively, whereas for fFN they were 1.22 and 0.98, respectively, indicating that fFN did not offer any additional predictive value. Conclusion In patients being treated with 17P, cervical length at 22-32 weeks is predictive of recurrent preterm birth, but fetal fibronectin is not.