Abstract Body: Background: Pregnancy-related complications increase risk for long-term cardiovascular (CV) disease. Environmental exposures such as fine particulate matter (PM_2.5) and extreme heat may exacerbate these risks through oxidative stress and inflammation, yet their relationships with perinatal health remain poorly understood. We examined how environmental and psychosocial factors jointly influenced gestational weight gain (GWG), postpartum weight retention (PPWR), and adverse pregnancy outcomes (APOs), including gestational diabetes, preeclampsia, and preterm birth, among a California cohort.

Methods: Data were drawn from 303 participants in the GROWell trial, a mobile lifestyle intervention for pregnant and postpartum women with overweight or obesity. Structural equation models (SEMs) tested hypothesized pathways between environmental exposures (latent factors for PM_2.5 and extreme heat over 7-, 30-, and 90-day periods), behavioral and psychosocial variables (diet, physical activity, anxiety), sociodemographics, and maternal outcomes (GWG, PPWR, APOs).

Results: Model fit was excellent for both GWG (CFI = 0.88, RMSEA = 0.047) and PPWR (CFI = 0.87, RMSEA = 0.049). Higher PM_2.5 exposure predicted lower GWG (β = –0.19, p = 0.01), while greater physical activity (β = –0.11, p = 0.048) and older age (β = –0.16, p = 0.005) also predicted less gain. Extreme heat was not directly related to GWG but increased odds of APOs (β = 0.22, p = 0.04). In the PPWR model, neither PM_2.5 nor heat predicted weight retention. Anxiety symptoms showed a borderline association with lower PPWR (β = –0.13, p = 0.05). Non-White participants experienced higher PM_2.5 exposure (β = –0.18, p = 0.03), reflecting environmental inequities.

Conclusions: Extreme heat increased risk for APOs, whereas higher PM_2.5 exposure was inversely related to GWG. Neither environmental exposure directly predicted PPWR, suggesting complex, time-specific pathways may link environmental stressors to maternal CV risk. Results highlight the need for interventions that address both lifestyle and structural drivers of CV risk across the perinatal continuum. Mobile lifestyle applications could be adapted to provide alerts to users when they are in high heat and high pollution environments to improve maternal outcomes.