A MODEL FOR INVESTIGATING MICROSCOPIC CHANGES INDUCED BY PROSTAGLANDIN-E(2) IN THE TERM CERVIX

Objective: The purposes of this study were twofold: to examine microsc opic changes in the term cervix after prostaglandin E2 (PGE2) using th e rabbit model, and to determine the lowest dose of PGE2 that would co nsistently prompt microscopic change as a basis for future investigati on. Methods: Twenty-four New Zealand white rabbits were administered e ither a placebo or PGE2 gel using hysteroscopic guidance in a blind ra ndomized manner. Twelve served as placebo gel-treated controls-six at 27 days of gestation and six at 29 days, shortly before the anticipate d time of early labor. Prostaglandin E2 gel was instilled in the remai ning 12 rabbits at day 27 using either a 0.04 mg/kg or 0.08 mg/kg dose which are the human body weight equivalents for cervical ripening. Mi croscopic changes in the cervix were evaluated by two pathologists in a blind manner, then compared using analyses of variance testing. Resu lts: Compared with the day 27 control group, microscopic changes in th e day 29 control group were more apparent for the presence of submucos al edema (P = 0.03), dissolution of collagen bundles (P = 0.01), and p resence of multinucleated histiocytes (P = 0.001). Microscopic changes in the cervix after use of the higher prostaglandin E2 dose on day 27 were more apparent than after using the lower dose and were indisting uishable from the day 29 controls. Conclusion: Using the gravid rabbit near term, PGE2 applied near the cervical os stimulated in a dose-dep endent manner the same microscopic changes in the cervical connective tissue as those found during early labor. These findings using the 0.0 8 mg/kg dose should serve in future investigations to answer clinical questions pertaining to cervical ripening.