In the current study, we took advantage of a preterm birth model induced by transvaginal injection of LPS into the cervix, which mimics the pathological condition of chorioamnionitis, and found that LPS-induced production of IL-1β, IL-6, TNF-α, and the murine IL-8 homologue, CXCL2, was demonstrably reduced in ASK1−/− mice compared to WT mice, as was the number of infiltrating uterine macrophages. This evidence concerns the gene MAP3K5 and chorioamnionitis.