Cervical ripening after treatment with prostaglandin E2 or antiprogestin (RU486). Possible mechanisms in relation to gonadal steroids.

OBJECTIVE

To compare the mechanisms for cervical ripening after treatment with prostaglandin E2 or antiprogestin (RU486) to spontaneous cervical ripening, with focus on gonadal steroid receptors.

STUDY DESIGN

Cervical biopsies were obtained from postpartal women after treatment with prostaglandin E2 (n=10), or antiprogestin (n=5). Postpartal women after spontaneous cervical ripening (n=10) served as controls. Levels of estrogen and progesterone receptors, their mRNAs, insulin-like growth factor I mRNA and serum estradiol and progesterone were quantitated. The collagen concentration and solubility by pepsin were determined. Statistical tests used were Kruskal-Wallis and Mann-Whitney U test.

RESULTS

After prostaglandin E2 treatment the collagen concentration was higher (P<0.05) as compared to spontaneous ripening. After antiprogestin treatment the estrogen receptor concentration was higher (P<0.05) in comparison to spontaneous ripening.

CONCLUSION

The elevated estrogen receptor concentration after antiprogestin treatment, in contrast to spontaneous ripening, and prostaglandin E2 treatment, indicates a that a receptor-mediated progesterone withdrawal does not explain the events behind spontaneous cervical ripening at parturition.