Changed proteoglycan metabolism in human cervix immediately after spontaneous vaginal delivery.

OBJECTIVE: To investigate whether the final cervical ripening just before or during labor corresponds to changes in cervical connective tissue metabolism and composition.
METHODS: Cervical biopsies taken transvaginally immediately after normal vaginal delivery and at hysterectomy were incubated with [35S] sulfate. In other biopsy specimens, the nonlabeled proteoglycan pattern was studied. Collagen concentration and organization were monitored to estimate the degree of cervical ripeness. Labeled and nonlabeled proteoglycans were isolated, characterized, and quantitated. Collagen concentration and collagen, extractable and not extractable by pepsin digestion, were quantitated as hydroxyproline.
RESULTS: A marked increase in the accumulation rate of labeled proteoglycans was observed in cervical biopsies obtained immediately after vaginal delivery. This increase was markedly larger than that previously noted in term pregnant women with unfavorable cervices. In particular, the accumulation of one labeled large chondroitin sulfate proteoglycan and one small dermatan sulfate proteoglycan, biglycan, increased significantly compared with the unfavorable cervices. In contrast, the small dermatan sulfate proteoglycan, decorin, showed a relative decrease. The changed synthesis of proteoglycans resulted in a two- to threefold increase in chemical amounts of the large proteoglycan, while the small dermatan sulfate proteoglycans decreased to approximately half of that in the nonpregnant cervix.
CONCLUSION: The changed cervical proteoglycan metabolism results in a changed proteoglycan composition of the tissue. This alteration probably influences collagen organization, contributing to the cervical softening and dilatation essential for an uncomplicated vaginal delivery.