Quantitative fetal fibronectin screening in asymptomatic high-risk patients and the spectrum of risk for recurrent preterm delivery

OBJECTIVE: We sought to determine whether a single quantitative vaginal fetal fibronectin (fFN) test at 24 weeks' gestational age (GA) can delineate the spectrum of risk of spontaneous preterm delivery (sPTD) in an asymptomatic high-risk population comprised of patients with a prior preterm birth. STUDY DESIGN: We performed a secondary analysis of a prospectively collected dataset in asymptomatic patients at high risk with singleton gestations who underwent quantitative fFN screening at 24 weeks. Data from 563 women with a history of preterm delivery (PTD) were available. The association between quantitative fFN concentrations collected at 24 weeks and subsequent GA at delivery was analyzed. RESULTS: The overall PTD rate < 34 weeks and < 37 weeks was 6.7% and 19.7%, respectively. In all, 497 of 563 patients (88%) at 24 weeks had an fFN level of 0 ng/mL. As the fFN concentrations in-creased, sPTD rates progressively increased. Compared with the fFN 0 ng/mL group, the relative risk for sPTD < 34 weeks was sequentially increased in each group, respectively: 2.42 (fFN 1-49 ng/mL; 95% confidence interval [CI], 0.76-5.66), 4.68 (fFN 50-199 ng/mL; 95% CI, 1.28-10.95), and 9.94 (fFN > 200 ng/mL; 95% CI, 2.90-19.67). Similar trends were seen between groups at different GAs from 32-37 weeks. CONCLUSION: In asymptomatic women with a prior PTD, quantitative fFN assessment at 24 weeks effectively delineates the risk of recurrent sPTD. Quantification of fFN may provide additional information regarding the spectrum of risk of subsequent sPTD than would be derived from the standard qualitative screen currently used.