We sought to determine whether connexin 43 (Cx43), the major myometrial gap junction protein, is differentially expressed in normal versus dysfunctional labor.Myometrial biopsies were obtained from 28 patients undergoing cesarean section and grouped into the following categories: (1) no labor, (2) dysfunctional labor, and (3) normal labor. Northern and Western analyses were performed to determine Cx43 messenger RNA (mRNA) and protein expression, respectively. Localization of Cx43 protein was determined by immunohistochemistry.Labor was associated with increased Cx43 mRNA expression (P .05).Dysfunctional labor is not associated with aberrant Cx43 mRNA or protein expression or with a reduction in immunodetectable Cx43 gap junctions.