Untimely rupture of the fetal membranes (FMs) is a major precipitant of preterm birth. Although the mechanism of FM weakening leading to rupture is not completely understood, proinflammatory cytokines, including tumor necrosis factor (TNF) and interleukin 1 beta (IL1B), have been shown to weaken FMs concomitant with the induction of reactive oxygen species, collagen remodeling, and prostaglandin release. We hypothesized that alpha-lipoic acid, a dietary antioxidant, may block the effect of inflammatory mediators and thereby inhibit FM weakening. Full-thickness FM fragments were incubated with control media or TNF, with or without alpha-lipoic acid pretreatment. Fetal membrane rupture strength and the release of matrix metalloproteinase 9 (MMP9) and prostaglandin E₂ (PGE₂) from the full-thickness FM fragments were determined. The two constituent cell populations in amnion, the mechanically strongest FM component, were similarly examined. Amnion epithelial and mesenchymal cells were treated with TNF or IL1B, with or without alpha-lipoic acid pretreatment. MMP9 and PGE₂ were analyzed by ELISA, Western blot, and zymography. TNF decreased FM rupture strength 50% while increasing MMP9 and PGE₂ release. Lipoic acid inhibited these TNF-induced effects. Lipoic acid pretreatment also inhibited TNF- and IL1B-induced increases in MMP9 protein activity and release in amnion epithelial cells, as well as PGE₂ increases in both amnion epithelial and mesenchymal cells. In summary, lipoic acid pretreatment inhibited TNF-induced weakening of FM and cytokine-induced MMP9 and PGE₂ in both intact FM and amnion cells. We speculate that dietary supplementation with alpha-lipoic acid might prove clinically useful in prevention of preterm premature rupture of fetal membranes.