Objective: Our purpose was to compare the level of expression of both type 1 and type 2 cyclooxygenase genes before and after labor and to localize their expression within the fetal membranes.
Study design: The sites of type 2 and type 1 cyclooxygenase messenger ribonucleic acid synthesis were identified with in situ hybridization. Expression of both types 1 and 2 cyclooxygenase was studied by reverse transcriptase polymerase chain reaction.
Results: Cyclooxygenase type 2 and type 1 expression was localized within the amniotic epithelium and amniotic mesoderm. Type 1 but not type 2 enzyme was also expressed in the chorionic mesoderm. Expression of the type 2 enzyme was significantly increased with the onset of labor. Type 1 enzyme expression did not significantly change with labor.
Conclusion: It is most likely that it is the inducible type 2 cyclooxygenase enzyme that mediates the increase in prostaglandin synthesis in amnion with the onset of labor.