Collagen metabolism in normal and complicated pregnancy: changes in the aminoterminal propeptide of type III procollagen in serum

The turnover of type III collagen, a major constituent of the myometrium and the uterine cervix, during pregnancy was evaluated by monitoring serum antigens related to the aminoterminal propeptide of type III procollagen. Their concentration increased markedly towards term in most uncomplicated pregnancies, while their size distribution throughout the pregnancy resembled that seen in the sera of normal healthy persons. In some patients, however, the level remained low, indicating interindividual variation in the release into serum and metabolism of the propeptide. There were no distinct changes during or immediately after vaginal delivery. Values exceeding the reference range for uncomplicated pregnancies were found during weeks 28-37 in patients with pre-eclampsia, essential hypertension, intrahepatic cholestasis of pregnancy or twin pregnancy. Thus, pregnancy should be taken into account when evaluating results of the serum assay for the aminopropeptide and the use of this assay as an indicator of pregnancy complications warrants further study.