The role of mobility and air-conditioning in prenatal temperature exposure and birth outcomes: A prospective birth cohort study in Guangzhou.

Climate change has heightened awareness of the health impacts of non-optimal temperatures (cold and heat), including the effect of gestational exposure and birth outcomes. However, temperature exposure assessment remains methodologically challenging due to unaccounted individual spatiotemporal mobility and adaptive behaviors, a gap that has not been adequately addressed in published studies. Using data from a prospective birth cohort in Guangzhou, China, conducted from 2017 to 2020, we assessed and compared three different exposure measures: home-based exposure, derived solely from ambient temperature data at residential locations; mobility-based exposure, incorporating individuals' spatiotemporal activities to capture dynamic environmental conditions; and AC & mobility-based exposure, an extension of the mobility-based approach that further integrates data on air-conditioning usage. We further evaluated the impact of these exposure assessments on the association between prenatal non-optimal temperature and adverse birth outcomes. Defining heat and cold by hours spent outside the optimal temperature range, we found mean mobility-based prenatal heat exposure of 6.14 hours and cold exposure of 3.59 hours, closely mirroring home-based levels. In contrast, AC & mobility-based exposures were significantly lower (heat: 2.09 hours; cold: 0.81 hours). Both home-based and mobility-based exposure were linked to increased risks of preterm birth and lower birth weight, however, among those remaining exposed, heat or cold exposure remained associated with adverse birth outcomes when air-conditioning use was considered. Evidence from this study suggests that adaptive behaviors, rather than routine mobility, play a crucial role in reducing prenatal exposure to extreme temperatures, mitigating the risks of adverse birth outcomes. Our study proposes a strategy to refine temperature exposure assessment in future large-scale, long-term epidemiological studies through the integration of air-conditioning use.