Human cervical remodelling during parturition is thought to depend principally on local collagenase activity originating mainly from polymorphonuclear leukocytes. The hypothesis to be tested was whether collagenase activity within granules of polymorphonuclear leukocytes is markedly increased at the time of delivery. Polymorphonuclear leukocytes collagenase activity in pregnant and non-pregnant women was measured by a method using [3H] labelled telopeptide free type I collagen. Collagenase activity in polymorphonuclear leukocytes immediately post-partum was higher than in non-pregnant patients. After delivery almost all the extracted collagenase was active when compared to that of late gestation. The number of leukocytes and the percentage of neutrophils were significantly higher than in non-pregnant patients. An increase in polymorphonuclear leukocyte collagenase activity at the time of parturition might be responsible for the proper timing of collagen breakdown within the uterine cervix.

Keywords: collagenase, polymorphonuclear leukocytes, cervical dilatati