ObjectiveTo determine the expression and localization of cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1), E-selectin, platelet–endothelial cell adhesion molecule (PECAM), and vascular cell adhesion molecule (VCAM) in the cervix and myometrium during pregnancy and labor.MethodsBiopsies of myometrium and cervix were obtained from non-pregnant women and from pregnant women before and after onset of spontaneous labor at term. Cell adhesion molecule mRNA expression was quantified using Northern blotting and cell adhesion molecule protein was localized using immunohistochemistry.ResultsICAM-1 mRNA was upregulated in the cervix (10-fold increase,P< .01) and myometrium (10.5-fold increase,P< .01) during labor. ICAM-1 was localized in the vascular endothelium and in leukocytes in the cervix and myometrium from all three groups of women. VCAM mRNA was upregulated in the cervix (2.5-fold increase,P< .01) during pregnancy and there was no further change during labor. VCAM localized weakly to the vascular endothelium in cervical and myometrial biopsies from pregnant and non-pregnant women. PECAM mRNA was significantly upregulated in myometrium during pregnancy (ninefold increase,P< .01) and did not change with the onset of labor. PECAM localized to the vascular endothelium in all cervical and myometrial biopsies and was identified on leukocytes. There were no significant changes in E-selectin mRNA expression in either tissue with pregnancy or parturition.ConclusionCell adhesion molecule expression changes in human cervix and myometrium during pregnancy and parturition. At least part of these changes are attributable to expression by leukocytes infiltrating these tissues.