Objective: This study was undertaken to determine which genes were up-regulated by acute distention in an amniotic epithelial cell line and in human fetal membranes. Study Design: WISH cells, a human amniotic epithelial cell line, were grown on silicone elastomer sheets coated with extracellular matrix and reproducibly distended by 40% in a novel device for 4 hours. Differential gene expression was analyzed by means of suppression subtractive hybridization. Expression of the identified genes was then quantitated by Northern blot analysis in fetal membrane explants after distention in the same device for 4 hours. The effect of distention on apoptosis of the cells and tissue samples was concomitantly studied by means of the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling method. Results: The genes for interleukin 8 and pre–B-cell colony-enhancing factor were found to be up-regulated in both the WISH cells and the distended fetal membranes. The apoptotic index values in both the cells and the tissue samples were unaffected by distention. Conclusions: Acute distention induces the up-regulation of interleukin 8 and pre–B-cell colony-enhancing factor in both WISH cells and human fetal membranes and does not cause apoptosis. (Am J Obstet Gynecol 2000;182:50-9.)