Background

Living in higher greenness level community has many benefits for pregnancy outcomes, however, few research have explored the relationship between greenness and spontaneous abortion (SAB). We aimed to analyze relationships between SAB and community greenness in Chinese pregnant women, and further assessed the modifying effects from air pollutants.

Methods

We studied 90 890 pregnant women from the China Birth Cohort Study from February 2018 to December 2021. We diagnosed SAB by certified obstetricians and gynecologists. The level of exposure to greenness during the first trimester was measured using the normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI). Particulate matter ≤ 2.5 μm (PM_2.5), nitrogen dioxide (NO₂) and ozone (O₃) were used as proxies of ambient air pollution. Time-dependent multivariable adjusted Cox proportional hazards models, with gestational weeks as the time scale, were used to analyze the association between SAB and greenness. We additionally performed subgroup analyses stratified by age, urbanicity, research location, season of birth, temperature, humidity and air pollution levels.

Results

Lower SAB prevalence was related to living in greener places. A 0.1 unit increase in NDVI_500m and EVI_500m was significantly associated with a 12.3% (95% CI 9.9%, 15.5%) and 16.2% (95% CI 11.4%, 20.6%) lower risks of SAB, respectively. In sensitivity analysis, these relationships remained consistent. The associations were stronger among older, participants lived in the north of China and lived in places with higher PM_2.5 and lower NO₂ levels.

Conclusions

Our findings indicate significantly inverse associations between community greenness and SAB in Chinese pregnant women, especially for older and participants who live in the north of China, the PM_2.5 and NO₂ may modify the effects of greenness on SAB.