Objective: To assess the safety of vaginal recombinant human relaxin in pregnant women treated before the induction of labor and to collect preliminary data on the efficacy of recombinant human relaxin in promoting cervical ripening.
Methods: In a multi-center, randomized, double-blind placebo-controlled trial, 40 women were studied before induction of labor because of post-dates. The women were randomized to receive either 1.5 mg recombinant human relaxin in 3% methylcellulose gel or gel only, placed into the posterior vaginal fornix after a cervical assessment on the evening before scheduled induction. If a subject did not go into spontaneous labor overnight, another cervical assessment was performed 15 hours following treatment, immediately before the standard induction regimen of the hospital.
Results: No important maternal or fetal-neonatal complications could be attributed to the drug. The differences between the recombinant human relaxin group and the placebo group for all the outcome measures of efficacy did not achieve statistical significance. Placebo patients were more likely to report moderate or strong uterine contractions in the first 4 hours following treatment than were the recombinant human relaxin-treated patients.
Conclusions: The use of recombinant human relaxin at a dose of 1.5 mg was not associated with any significant maternal or fetal-neonatal complications. The relatively small number of subjects in this study was chosen deliberately because this was the first use of the drug in pregnant subjects. Assessment of efficacy will require studies that include more patients and a range of relaxin doses.