Collagen changes in the human uterine cervix at parturition.

Abstract Five specimens were taken from the uterine cervix immediately post partum, one specimen was taken before onset of labor, and one was taken at 16 weeks' pregnancy for comparison with five surgical specimens taken from the cervix during the proliferative phase of the menstrual cycle. Cervical collagen, including the reducible cross-links in the acetic acid-soluble and insoluble fractions, was studied. Samples taken from nonpregnant women and from women during delivery could not be differentiated using the ratio of hydroxyproline/total protein as an index of collagen in the soluble fractions. However, after electrophoresis, intense bands corresponding to collagen chains were seen in the proliferative phase and during early pregnancy, whereas only small amounts of intact collagen chains could be detected ante- and intrapartum, indicating the prevalence of collagen breakdown products. In the insoluble fractions the hydroxyproline/total protein ratio drops from 0.75 in the samples from the nonpregnant group to 0.35 in the intrapartum samples. The typing of collagen in the insoluble fraction showed the predominance of type I collagen. Twenty to 38 per cent of collagen present was type III. No striking difference was seen in the analysis of reducible cross-links between the groups. These data show that cervical collagen undergoes significant biochemical changes that might play an important role in cervical dilatation.