Pyroptosis, inflammatory programmed cell death, is initiated through the inflammasome and relies on the pore-forming actions of the effector molecule gasdermin D. Herein, we investigated whether gasdermin D is detected in women with spontaneous preterm labor and sterile intra-amniotic inflammation or intra-amniotic infection.Amniotic fluid samples (n = 124) from women with spontaneous preterm labor were subdivided into the following groups: 1) those who delivered at term (n = 32); and those who delivered preterm 2) without intra-amniotic inflammation (n = 41), 3) with sterile intra-amniotic inflammation (n = 32), or 4) with intra-amniotic infection (n = 19), based on amniotic fluid IL-6 concentrations and microbiological status of amniotic fluid (culture and PCR/ESI-MS). Gasdermin D concentrations were measured using an ELISA kit. Multiplex immunofluorescence staining was also performed to determine the expression of gasdermin D, caspase-1, and interleukin-1β in the chorioamniotic membranes. Detection of pyroptosis (active caspase-1) in decidual cells from women with preterm labor and birth was performed using flow cytometry.1) Gasdermin D was detected in the amniotic fluid and chorioamniotic membranes from women who underwent spontaneous preterm labor/birth with either sterile intra-amniotic inflammation or intra-amniotic infection, but was rarely detected in those without intra-amniotic inflammation. 2) Amniotic fluid concentrations of gasdermin D were higher in women with intra-amniotic infection than in those with sterile intra-amniotic inflammation, and its expression in the chorioamniotic membranes was associated with caspase-1 and IL-1β (inflammasome mediators). 3) Decidual stromal cells and leukocytes isolated from women with preterm labor and birth are capable of undergoing pyroptosis since they expressed active caspase-1.Pyroptosis can occur in the context of sterile intra-amniotic inflammation and intra-amniotic infection in patients with spontaneous preterm labor and birth. This article is protected by copyright. All rights reserved.