The stretch modulus of human cervical tissue in spontaneous, oxytocin-induced, and prostaglandin E2-induced labor.

A total of 62 strips of cervical tissue from 28 patients at term were tested for stiffness (stretch modulus) by elongation and measuring the tension produced by a given stretch. The stretch modulus was taken as the slope of the linear regression curve derived from the linear portion of the stress-strain relationship. The data were obtained from three patient categories: (1) 17 strips from seven patients undergoing spontaneous labor, (2) 18 strips form 10 patients with labor induced by PGE2, and (3) 27 strips from 11 patients with labor induced by oxytocin. The stretch moduli of cervical tissue obtained from spontaneous and oxytocin-induced labor patients were similar. The stretch moduli of cervical tissue obtained from PGE2-induced labor patients were significantly lower than those from either the spontaneous or the oxytocin-induced labor groups. These results show that PGE2, when used for induction of labor at term, has the ability to lower the stiffness of cervical tissue. This property of prostaglandin may be useful therapeutically for the indicated induction of labor in patients with an unfavorable cervix.