The integrity of cervical collagen during pregnancy and labor.

The concentration of collagen in the human uterine cervix decreases during pregnancy. This change contributes to the ripening process, which facilitates cervical dilatation during labor. It has been suggested that cervical collagen is partly degraded at term and after delivery. In order to evaluate this hypothesis we investigated the proportion of intact to degraded collagen after solubilization of about 86% of the collagen with pepsin in acetic acid. Total collagen was quantitated as hydroxyproline whereas intact collagen was estimated by SDS-gel electrophoresis. The proportion of intact collagen to total collagen did not change during pregnancy and delivery. Furthermore it was similar to that of intact standard collagen. Thus, even if the concentration of collagen is diminished during pregnancy as a result of increased collagenolytic activity, there is no indication of a qualitative change of the remaining collagen.