Prolonged induction of labor is problematic for patients and providers alike, but we lack clin. tools to help predict time to delivery. We hypothesize quant. fetal fibronectin may function as a tool to predict prolonged induction. We performed a prospective observational study of low-risk patients undergoing induction of labor at 39 0/7 to 41 0/7 wk. Prior to induction, fetal fibronectin (fFN) sampling (off-label use) and transvaginal cervix length were completed. Median fFN values were compared to time-to-delivery using 12-, 24-, and 36-h thresholds. Delivery within these thresholds was modeled using logistic regression after controlling for parity, Bishop score, cervical length, and gestational age. Continuous log time-to-delivery was modeled using linear regression. Arrowhead Regional Medical Center IRB granted approval Protocol #21-29. Of 95 patients enrolled, 35 (37%), 70 (74%), and 80 (84%) patients delivered within 12, 24, and 36 h. Unadjusted tests for differences in median fFN in these groups were nonsignificant. Cervical length and gestational age were removed from adjusted models because of nonsignificance. Regression models showed a significant relationship between fFN and delivery time within 24 h, but not within 12 or 36 h. Each 50 ng/mL increase in fFN was associated with 25% higher odds of delivering within 24 h (adjusted odds ratio [aOR] 1.25, 95% CI 1.01-1.54, P=.04) with a 3.7% decrease in labor time (53-min reduction in a 24-h labor) (aOR 0.963, 95% CI 0.929-0.097, P=.04). Our findings suggest fFN maybe a useful tool to identify patients who will deliver within 24 h of induction initiation.