Synthesis of oxytocin in amnion, chorion and deciduas may influence the timing of human parturition. J Clin Investig 91:185–192

Despite the widespread clinical use of oxytocin (OT) as a po-tent and specific stimulant of labor, previous research data have not supported a role for OT in the physiology of normal human parturition. We have demonstrated synthesis of OT mRNA in amnion, chorion, and decidua using Northern blot analysis, ribo-nuclease protection assays, and in situ hybridization. Probes directed towards both the 3 ' and 5 ' ends of the gene have been used. Levels were highest in decidua with considerably less in chorion and amnion and very low levels in placenta. The tran-script size in decidua appears to be 60-80 nucleotides smaller than the transcripts in amnion and chorion. OT gene expression in chorio-decidual tissues increased three- to fourfold around the time of labor onset. Estradiol stimulated synthesis of OT mRNA during in vitro incubation. These results support the hypothesis of a paracrine system involving OT and sex steroids within intrauterine tissues wherein significant changes could occur without being reflected in the maternal circulation. Such a paracrine system could rationalize a long-sought role for oxy-tocin in the physiology of human labor. These data may lead to novel approaches towards prevention or treatment of preter