Objective: In 2012, two Kaiser Permanente Northern California (KPNC) hospitals began offering outpatient cervical ripening with oral misoprostol under a study protocol. We evaluated inpatient time from admission to delivery and adverse maternal and neonatal outcomes associated with outpatient use of misoprostol for cervical ripening among low-risk women with term pregnancies., Study Design: We conducted a retrospective cohort study comparing three groups: women who received misoprostol (1) outpatient, under a study protocol; (2) inpatient, at the study sites; and (3) inpatient, at all KPNC hospitals. Data were obtained from between 2012 and 2017. The primary outcome was time from inpatient admission to delivery. Secondarily, we evaluated maternal and neonatal outcomes, including the duration and maximum rate of oxytocin administered, rate of cesarean delivery, incidence of chorioamnionitis and blood transfusion, Apgar scores, and neonatal intensive care unit admissions. Demographic and clinical characteristics and outcomes of the outpatient group were compared with both inpatient misoprostol groups using the appropriate statistical test. Variables included in the regression analysis were either statistically significant in the bivariate analyses or have been reported in the literature to be potential confounders: maternal age at admission, race/ethnicity, body mass index, cervical dilation at initial misoprostol, and parity., Results: We analyzed data from 10,253 patients: (1) 345 outpatients, under a study protocol; (2) 1,374 inpatients, at the study sites; and (3) 9,908 inpatients, at all the Kaiser hospitals. Women in the outpatient group were more likely to be white than both inpatient groups (63.3 vs. 56.3% at study sites and 47.1% in all hospitals, p = 0.002 and <0.001, respectively); other demographics were clinically comparable. Most women undergoing labor induction were nulliparous; however, a greater proportion in the outpatient group were nulliparous compared with inpatient groups (70.8 vs. 61.8% and 64.3%, p = 0.002 and 0.01). On inpatient admission for delivery, women who received outpatient misoprostol were more likely to have a cervical dilation of ≥3 cm (39.8 vs. 12.5% at study sites and 9.7% at all KPNC hospitals, p < 0.001 for both). The outpatient group had a shorter mean time between admission and delivery (23.6 vs. 29.4 at study sites and 29.8 hours at all KPNC, p < 0.001 for both). The adjusted estimated mean difference between the outpatient and inpatient group at all the Kaiser hospitals in time from admission to delivery was -6.48 hours ( p < 0.001), and the adjusted estimated mean difference in cervical dilation on admission was +1.02 cm ( p < 0.001). There was no difference in cesarean delivery rates between groups. The rate of chorioamnionitis in the outpatient group was higher compared with inpatients at all hospitals (17.7 vs. 10.6%, p < 0 . 001), but similar when compared with the inpatients at the study sites (17.7 vs. 15.4%, p = 0.29)., Conclusion: Outpatient use of misoprostol for cervical ripening under the study protocol was associated with reduced inpatient time from admission to delivery compared with inpatient misoprostol. Although there was a higher rate of chorioamnionitis among outpatients under the study protocol compared with inpatients at all hospitals, there was no difference when compared with inpatients at the study sites. There was no difference in rates of cesarean delivery or maternal or neonatal complications with outpatient misoprostol., Key Points: · Outpatient misoprostol patients had 6.46 fewer hours from admission to delivery compared with inpatients at all hospitals.. · There was no difference in the rate of cesareans between the outpatient versus inpatient misoprostol groups.. · Other maternal and neonatal complications were low and comparable among outpatients and inpatients who received misoprostol; this study was not large enough to assess rare safety outcomes.., Competing Interests: None declared., (Thieme. All rights reserved.)