Recombinant human relaxin as a cervical ripening agent

Objective The aim of this study was to investigate the efficacy and safety of recombinant human relaxin (rhRIx) as a cervical ripening agent in women with an unfavourable cervix before induction of labour at term.
Design A multi-centre, double-blind, placebo-controlled trial performed in Edinburgh, Glasgow and Oxford. Women were treated with 0, 1, 2 or 4 mg of rhRIx in a gel vehicle administered intravaginally. Analysis of variance tests were performed on all continuous variables, and Cochran Mantel-Haenszel tests employed for all discrete variables.
Participants Ninety-six women at 37 to 42 weeks of gestation with a singleton pregnancy and a modified Bishop score of 4 were recruited.
Results There was no significant difference in the change in modified Bishop score between the four treatment groups. The lengths of the first and second stages of labour were similar in all 4 groups. PGE₂ and oxytocin requirements were similar in all groups, as was the mode of delivery. There was no evidence that relaxin was absorbed systemically when given in this way.
Conclusion Recombinant human relaxin 1 to 4 mg, administered as an intravaginal gel, has no effect as a cervical ripening agent before induction of labour at term.