Objective: This study was undertaken to identify genes with expression up-regulated by acute distention in the human fetal membranes. Study Design: Fetal membrane explants were distended reproducibly in a novel device in vitro for 4 hours, and suppression subtractive hybridization was used to identify the candidate genes for up-regulation of expression in response to this stimulus. The up-regulation in response to distention was confirmed by quantitative Northern blot analysis both after a 4-hour in vitro distention and after labor in vivo. Results: Suppression subtractive hybridization identified 3 genes with expression up-regulated by acute distention: an interferon-stimulated gene encoding a 54-kd protein, the gene for huntingtin-interacting protein 2 (a ubiquitin-conjugating enzyme), and a novel transcript. Expression of each of the distention-responsive genes found to be up-regulated in vitro was also up-regulated in fetal membranes in association with labor. Conclusions: Suppression subtractive hybridization was successfully applied to a complex tissue, the human fetal membranes, and 3 novel distention-responsive genes were identified. Both acute in vitro distention and labor in vivo up-regulate expression of at least 3 genes in the human fetal membranes. (Am J Obstet Gynecol 2000;182:60-7.)