Induction of labour in nulliparous and multiparous women: a UK, multicentre, open-label study of intravaginal misoprostol in comparison with dinoprostone

Objective To compare the efficacy and safety of a 25-microgram vaginal tablet of misoprostol (APL202) with dinoprostone (3-mg vaginal tablet) in cervical ripening and labour induction.

Design A randomised, open-label, noninferiority, comparative study in two maternal populations.

Setting Eighteen NHS study centres across the UK.

Population Nulliparous or multiparous women with a singleton pregnancy eligible for induction of labour.

Methods Women were randomised to receive either misoprostol, initially 25 micrograms (50 micrograms in nulliparous women with Bishop score <= 4) followed by 25 micrograms after 4 and 8 hours, or dinoprostone, initially 3 mg followed by 3 mg after 6 hours. Clinical noninferiority of misoprostol was defined as an absolute difference between treatments of no more than 10% for the primary outcome.

Main outcome measures The number of vaginal deliveries achieved within 24 hours of labour induction. Maternal and fetal safety outcomes.

Results A total of 626 women were randomised to misoprostol (n = 318) or dinoprostone (n = 308) treatment. The rate of vaginal deliveries achieved within 24 hours of induction did not significantly differ between the misoprostol and dinoprostone (43 versus 47%; 3.74% difference, 95% CI -3.58 to 11.05, respectively) treatment groups. The treatments were generally comparable for other secondary efficacy measures. Maternal and fetal adverse events were similarly distributed across the misoprostol and dinoprostone groups.

Conclusions Low-dose misoprostol is efficacious in cervical ripening and labour induction and demonstrates a similar fetal and maternal safety profile to dinoprostone.