Reconceptualizing chorioamnionitis as an immune-mediated inflammatory disorder at the maternal-fetal interface

Chorioamnionitis has long been regarded as an infection-driven obstetric disorder, yet converging clinical, pathological, and mechanistic evidence demonstrates that host-derived inflammatory pathways, together with microbial factors, critically shape placental injury, fetal involvement, and neonatal outcomes. Histological inflammation of the chorioamniotic membranes correlates more strongly with adverse outcomes than microbial detection alone, underscoring the importance of host immune responses even in the context of microbial invasion.

This review aims to synthesize current insights into the immune landscape of the maternal-fetal interface, the coordinated contributions of multiple immune pathways, the interplay between microbial and non-microbial triggers, and the downstream consequences for fetal and neonatal health. Rather than replacing the infection-based paradigm, we aim to extend it by integrating immunological mechanisms that account for disease heterogeneity and variable clinical outcomes.

A narrative review was conducted using a structured literature identification strategy. Relevant peer-reviewed original studies, review articles, clinical investigations, and translational studies were identified through targeted literature searches and synthesized according to their mechanistic and clinical relevance.

Sterile intra-amniotic inflammation can produce overlapping responses with infection, arising from partially distinct mechanisms and representing a context-dependent extension within infection-associated processes, without constituting a separate primary pathway. Advances in maternal-fetal immunology identify the maternal-fetal interface as a dynamic immune environment in which disrupted tolerance, heightened pattern-recognition signaling, and amplified cytokine and chemokine networks lower the threshold for pathological activation. Multiple pathways including interleukin-1 and interleukin-6 signaling, macrophage activation, and neutrophil-mediated responses collectively drive this process. In this context, neutrophil extracellular traps formation represents an important effector mechanism linking microbial and non-microbial cues to tissue-destructive inflammation. Fetal exposure to these pathways results in immune programming consistent with the fetal inflammatory response syndrome, contributing to pulmonary, intestinal, and neurodevelopmental sequelae. Although antibiotics remain essential for infection control, they do not directly target downstream immune circuits sustaining placental inflammation or fetal injury.

Reframing chorioamnionitis as an immune-mediated disorder, while preserving the central role of infection, supports endotype-based classification and targeted immunomodulation. It also highlights the potential of microbiota-informed strategies beyond pathogen eradication, with implications for preventing preterm birth and improving neonatal outcomes.