Ripening of the human cervix with porcine ovarian relaxin

Recent experience has suggested that porcine ovarian relaxin may promote cervical changes. We have performed two double-blind randomized studies: (1) comparing cervical changes with relaxin versus placebo during oxytocic labor induction and (2) as outpatients in postdates pregnancies. In the induction study, cervical changes were speeded up by both 2 and 4 mg doses of relaxin, and times to delivery were decreased. In the outpatient study, 2 mg doses of relaxin produced greater cervical changes than did control or 4 mg doses. We conclude that relaxin may have benefit in ripening of the cervix. Since relaxin works directly on the cervix and not through uterine contractions, relaxin have advantages in cervical ripening of pregnancies in which stress to the fetus is an issue.