Abstract
OBJECTIVE: The aim of the study was to compare two labor induction regimens (4 and 6 h), to determine predictors of successful labor induction with intravaginal misoprostol 25 μg tablets, and to evaluate the association with adverse perinatal outcomes. METHODS: This was a retrospective cohort study that included singleton pregnancies undergoing induction of labor with an intravaginal misoprostol 25 μg tablet between 37 and 42 weeks of gestation. The pregnant women were divided into two groups: Group 1-intravaginal misoprostol 25 μg every 4 h and Group 2-intravaginal misoprostol 25 μg every 6 h. RESULTS: Pregnant women were divided into Group 1 (n=289) and Group 2 (n=278). Group 1 had a higher median number of intravaginal misoprostol 25 μg tablets (3.0 vs. 2.0 tablets, p<0.001), a lower prevalence of postpartum hemorrhage (7.6 vs. 32.7%, p<0.001), and a higher need for oxytocin (odds ratio [OR]: 2.1, 95%CI: 1.47-2.98, p<0.001) than Group 2. Models including intravaginal misoprostol 25 μg tablets every 4 and 6 h [x2(1)=23.7, OR: 4.35, p<0.0001], parity [x2(3)=39.4, OR: 0.59, p=0.031], and Bishop's score [x2(4)=10.8, OR: 0.77, p=0.019] were the best predictors of failure of labor induction. A statistically significant difference between groups was observed between the use of the first intravaginal misoprostol 25 μg tablet at the beginning (Breslow p<0.001) and the end of the active labor phase (Long Hank p=0.002). CONCLUSION: Pregnant women who used intravaginal misoprostol 25 μg every 4 h had a longer time from the labor induction to the beginning of the active phase of labor and higher rates of adverse perinatal outcomes than women who used intravaginal misoprostol 25 μg every 6 h.