Trajectories of meteorological and air pollution exposures during pregnancy and risk of childhood asthma: A population-based cohort study.

The incidence of childhood asthma continues to rise in low-latitude tropical regions. Environmental exposure during pregnancy may affect fetal development through dynamic interaction, but existing studies are mostly limited to single environmental factor. This retrospective cohort study of 8,339 children aged 2-12 years in Sanya, China, utilized geographic information systems to link individual birth coordinates with high-resolution meteorological data, including temperature, precipitation, humidity, and solar radiation. Group-based trajectory modeling and group-based multi-trajectory modeling were applied to analyze exposure trajectories for multiple environmental variables across pregnancy trimesters: first trimester (1-3 months), second trimester (4-6 months), and third trimester (7-9 months). Multivariable logistic regression was performed to analyze the association between environmental trajectories and childhood asthma. Stratified analysis was conducted to evaluate the modification effect of sex and history of family allergy. Our findings reveal that high precipitation during the second and third trimesters (aOR = 1.43, 95%CI:1.04-1.98) and sustained high humidity throughout pregnancy (aOR = 2.29, 95%CI:1.06-5.25) were significantly associated with an increased risk of childhood asthma. First-trimester solar radiation alone was associated with a reduced risk (aOR = 0.54, 95%CI:0.29-1.02). However, multivariate trajectory analysis revealed that this benefit was offset when combined with high precipitation (>127.74 mm) in the second and third trimesters and persistent high humidity (>82.47%). This combined exposure pattern was associated with a 2.61-fold increased childhood asthma risk (95%CI:1.21-5.85). Stratified analysis showed that male (aOR = 7.20, P < 0.01) and children with family allergy history (aOR = 2.94, P < 0.05) were more sensitive to the combined exposure. These findings reveal a critical prenatal interaction: early solar radiation protection against childhood asthma is offset by later humidity and precipitation, informing targeted prevention in tropical areas.