DESCRIPTION OF TOPIC:
Chile is undergoing a fourth obstetric transition, a stage where biomedical advances coexist with new ecosocial risks. In this context, a growing and unexpected threat is emerging: the convergence of hypertensive pregnancy disorders, preterm birth, and air pollution. This triad represents a new type of obstetric emergency, especially in low-income urban areas such as northern Santiago, where particulate matter (PM₂.₅) levels chronically exceed 30 µg/m³, and critical air pollution episodes have doubled in the past decade. Preeclampsia remains one of the leading direct causes of maternal death in Chile, while preterm birth leads to neonatal mortality. Although recent studies have confirmed statistical associations between air pollution exposure and these adverse outcomes, the causal biological pathway—how polluted air damages the placenta and triggers systemic inflammation—remains unclear.

RELEVANCE TO MIDWIFERY:
This research-in-progress aims to contribute to that causal understanding through an innovative design combining population-scale epidemiology and biological plausibility. It analyzes a retrospective cohort of 60,000 births (2014–2024), georeferenced to estimate individual exposure to PM₂.₅ using the national SINCA system. A nested case–control study is also underway, analyzing inflammatory (CRP, IL-6, sFlt-1), epigenetic (DNA methylation) biomarkers, and the incidence of preeclampsia and preterm birth, in placental tissue, maternal blood, and cord blood. So far, 27 placentas have been collected, and samples are being processed. Preliminary findings—available for ICM 2026—will provide locally grounded evidence to support new clinical recommendations. In the climate crisis era, midwives are not only birth attendants: they are frontline defenders of reproductive justice and environmental health. Every prenatal counseling session that includes air quality is a bold act of midwifery advocacy for birthing in clean air. This proposal aligns with SDGs 3 (health), 11 (sustainable cities), and 13 (climate action). Ethics: Approved by CEISH 030-2024 Funding: Supported by FONDECYT 1240684 Conflicts of interest: None declared Workforce - sustainability 2 (including three-minute presentation competition)