Pre-induction cervical ripening with different initial doses of intravaginal misoprostol: time to delivery and peri-natal outcomes.

From 2016 to 2018, a total of 300 pregnant women underwent induction of labour. Those women were allocated in two groups according to the initial dose of misoprostol. Group I (150 women) received intravaginally 50 µg misoprostol followed by 25 µg every four hours, up to a maximum of four doses whereas in group II (150 women) the initial dose was 25 µg intravaginal followed by the same dose every four hours up to a maximum of four doses. Women with previous uterine scar, abnormal foetal heart rate, severe foetal malformation, foetal growth restriction or multiple pregnancy were excluded. The aim of study was to compare the effectiveness (hours until delivery) and perinatal outcomes of both schemes of cervical ripening. Initial doses of 50 µg of misoprostol reduced the time until delivery (17.65 ± 8.2 hours vs. 20.85 ± 9.3 hours; p=.007) and the need of oxytocin (34.6% vs. 46.67%; p=.046), compared to the use of 25 µg misoprostol in all doses. No differences were observed regarding perinatal outcomes.In conclusion, starting with 50 µg of misoprostol in the first dose reduced time to vaginal delivery and decreased the use of oxytocin without worse perinatal outcomes.Impact StatementWhat is already known on this subject? The rate of labour induction is increasing. Mechanical and medical methods try to establish the active phase of labour as quickly and safely as possible. For this reason, there are numerous studies assessing different protocols, dosages and indications.What do the results of this study add? Despite the numerous studies, due to ethical restrictions, it is difficult to carry out prospective studies. For this reason, studies like this help to establish the most appropriate dose of misoprostol in two of the most common indications for induction of labour. We demonstrated that increasing initial doses up to 50 mg of misoprostol are safer and more effective.What are the implications of these findings for clinical practice and/or further research? This study could be useful for future prospective and randomised studies as well for including these data in a meta-analysis. In addition, these results may update the clinical protocols and reduce hospital stay without worse perinatal outcomes.