321: Cervical ripening with hyaluronidase: effect on myometrial contractility in vivo and in vitro

Abstract

We have shown that intracervical injection of hyaluronidase can induce cervical ripening and accelerate parturition after induction of labor in rats. Hyaluronidase also affects the biophysical properties of the rat cervix consistent with augmented ripening. A common issue using cervical ripening agents is their concomitant effect on uterine activity. The objective of this study was to determine whether hyaluronidase causes an increase in uterine contractility. Timed pregnant Sprague-Dawley rats were injected intracervically with 100 I.U. of hyaluronidase or saline on day 18 of pregnancy (n=7 or 8 per group). All rats were euthanized at term. Uterine rings were isolated for isometric tension experiments. Cumulative dose response curves to oxytocin and hyaluronidase, as well as the maximum contractile response to KCl (60 mM) were obtained and compared between the two groups. There was no difference in the contractile response of rat myometrium to oxytocin between hyaluronidase treated animals and controls (figure). Similarly, exposure of the myometrium to increasing doses of hyaluronidase did not cause uterine contractions in either of the study groups (figure). There was no signifiacnt variation in the maximal myometrial response to KCl between groups. Despite its effect on cervical maturation, the use of hyaluronidase is not associated with an increase in uterine contractions or myometrial sensitivity to oxytocin. This makes hyaluronidase a potentially superior agent for pre-induction cervical ripening as compared to currently available agents. It may be a safer alternative in women with a history of a previous cesarean delivery, or a candidate for use in outpatient settings.