Cervical epithelia have numerous functions that include proliferation, differentiation, maintenance of fluid balance, protection from environmental hazards, and paracellular transport of solutes via tight junctions. Epithelial functions must be tightly regulated during pregnancy and parturition as the cervix undergoes extensive growth and remodeling. This study evaluated tight junction proteins as well as markers of epithelial cell differentiation in normal and cervical ripening defective mice to gain insights into how the permeability barrier is regulated during pregnancy and parturition. While numerous tight junction proteins are expressed in the nonpregnant cervix, claudin 1 and 2 are temporally regulated in pregnancy. Claudin 1 mRNA expression is increased while claudin 2 expression declines. The cellular localization of claudin 1 shifts at the end of pregnancy (gestation d18.75) to the plasma membrane in a lattice pattern consistent with tight junctions in the apical cells. The timing of claudin 1 enriched tight junctions coincides with initiation of terminal differentiation of cervical squamous epithelia as evidenced by the increased expression of genes by differentiated epithelia late on gestation d18. The cervical ripening defective steroid 5-reductase type 1 deficient mouse which has an elevated local progesterone concentration also has aberrant claudin 1 and 2 expressions, fails to form claudin 1 enriched tight junctions and lacks normal expression of genes involved in epithelial terminal differentiation. These data suggest that changes in permeability barrier properties during cervical ripening are in part negatively regulated by progesterone and that dynamic changes in barrier properties of the cervix occur during pregnancy and parturition.