OBJECTIVE: to compare maternal and neonatal outcomes using 25µg 2-hourly and 50µg 4-hourly oral Misoprostol for induction of labour (IOL) DESIGN: observational study SETTING: Tertiary care center, Amsterdam UMC, location VUmc, the Netherlands POPULATION: Women with a vital singleton pregnancy between 37+0 and 42+0-weeks of pregnancy with an indication for IOL with oral Misoprostol. METHODS: Retrospective cohort study using anonymous data from the Amsterdam UMC from 2016-2021. The current procedure (25µg every 2 hours, June 2018-March 2021) was compared to the former procedure (50µg every 4 hours, March 2016-May 2018). MAIN OUTCOME MEASURES: Primary outcome measure was caesarean section rate. Secondary outcome measures were a composite neonatal outcome (Apgar <
7 at 5 minutes and/or NICU admission) and uterine hyperstimulation. RESULTS: A total of 1002 women were included, 621 women using 25µg and 381 using 50µg oral Misoprostol. The composite neonatal outcome occurred significantly less in women using 25µg compared to those using 50µg (aOR 0.67, 95% CI 0.46-0.97). There was no significant difference in caesarean section rate between the two protocols (18.4% vs 21.5%, respectively, aOR 0.74, 95% CI 0.52-1.05). A single case of uterine hyperstimulation with fetal heartrate changes occurred after start of oxytocin where 25µg was used, whereas there was none with 50µg (0.1%, P=0.62). CONCLUSIONS: The caesarean section rate did not alter significantly. The IOL protocol using 25µg as compared to 50µg oral Misoprostol was associated with a significant decrease in the composite neonatal outcome. Low-dose oral Misoprostol could be a safe method for outpatient IOL, further research is needed, preferably by RCT's. FUNDING: None.