CYCLOOXYGENASE DISTRIBUTION IN HUMAN PLACENTA AND DECIDUA DOES HOT CHANGE WITH LABOR AFTER TERM OR PRETERM DELIVERY

Our objective was to determine, in an immunohistochemical study, the d istribution of cyclo-oxygenase in placental and decidual tissues befor e and after labour at varying gestations. Subjects were pregnant women undergoing singleton delivery after idiopathic preterm labour at less than 34 weeks' gestation (n = 13); spontaneous term labour at 37-42 w eeks' gestation (n = 11); preterm caesarean section at less than 34 we eks' gestation for pre-eclampsia or intrauterine growth retardation (n = 8), elective term caesarean section at 37-42 weeks' gestation for c ephalopelvic disproportion (n = 7). Within the placental basal plate c yclo-oxygenase was localised in decidual stromal cells, extravilious t rophoblast, and the apical border of villous syncytiotrophoblast, both before and after labour, regardless of gestational age. Within the pl acental membranes, decidual stromal cells showed intense cytoplasmic c ycle-oxygenase labelling and the chorion laeve strong membrane-associa ted cycle-oxygenase reactivity before and after labour, regardless of gestational age. The amnion showed a heterogeneous staining pattern. A fter labour at term there was either positive cytoplasmic (5/10) or ap ical staining (5/10). Cycle-oxygenase was demonstrated in an apical di stribution in only 50% of the other subject groups. Cyclo-oxygenase is present in both decidua and placental tissues prior to the onset of l abour at term. Demonstration of decidual and trophoblastic cyclo-oxyge nase in both preterm and term subjects suggests that differential avai lability of cyclo-oxygenase is unlikely to be important in preterm del ivery. Research into the withdrawal of inhibition or increased substra te availability is most likely to shed light on the signal pathways in volved in the onset of labour, regardless of gestation.