The purpose of this study was to assess the structural, biomechanical, and biochemical effects of mifepristone-induced progesterone withdrawal on the rat cervix to identify possible mechanisms by which mifepristone incites cervical ripening.

After the administration of mifepristone, cervical tensile strength was determined by the cervical creep method. With polarized light microscopy and transmission electron microscopy, collagen organization and microstructure were quantified. Matrix metalloproteinase expression was assessed by Western Blot and Real-time reverse transcriptase–polymerase chain reaction.

Mifepristone induced a decrease in cervical tensile strength at mid gestation that was associated with a decrease in collagen organization. Additionally, mifepristone led to collagen fragmentation with a significant decrease in fibril length and diameter, although fibril bundling remained unaffected. Matrix metalloproteinase-2 expression increased after the administration of mifepristone.

Mifepristone-induced cervical ripening is associated with collagen degradation, and the collagenase activity of matrix metalloproteinase-2 may play a role in this process.