Greenness Exposure And Low Birth Weight

Objective:Low birth weight(LBW)is a globally recognized public health issue and a major cause of infant mortality,with significant impacts on the health of children and adults.Though several studies have investigated the potential positive impact of greenness exposure during pregnancy in reducing the risk of LBW,existing studies have been largely conducted in high-income countries such as North America and Europe,with a lack of nationwide evidence in low-and middle-income countries where LBW is more prevalent.In this study,we aimed to quantify the risk and burden of LBW associated with greenness exposure during pregnancy using a nationwide database of Iranian live births,providing a data foundation and theoretical basis for greenness planning and LBW reduction goals in low-and middle-income countries.Methods : A total of 4021741 pregnant women and their live-born infants,collected by the Iranian Ministry of Health and Medical Education from 2013 to 2018,were selected as the study population.Normalized difference vegetation index(NDVI)and enhanced vegetation index(EVI)grid data with a spatiotemporal resolution of 16 days and 250×250 m were extracted from global vegetation index products generated by the Moderate Resolution Imaging Spectroradiometer.Based on the hospital address and gestational period of the pregnant women,the average NDVI and EVI exposure levels during pregnancy within multiple buffers(500 m,1000 m,2000 m,and 3000 m)were evaluated.The outcomes of interest were LBW and term low birth weight(TLBW).Multivariable-adjusted logistic regression models were employed to investigate the associations between LBW/TLBW and greenness exposures throughout pregnancy.To estimate the exposure-response functions,greenness exposures were fitted as a smooth term using restricted cubic splines.Subgroup analyses were done to evaluate potential effect modifiers,stratified by age(≤25,26–35,and >35),education level(below high school,high school,and above high school),and residence(city and village).Attributable burden of LBW and TLBW under scenarios of improved green space were estimated in Iran for the year 2015,through a counterfactual analysis.Results:Among the 4021741 live birth records included in the study,263728(6.6%)cases were LBW and 121852(3.0%)were TLBW.After adjusting for maternal sociodemographic characteristics,fetal variables,and environmental factors,significant and inverse associations were observed between LBW/TLBW and greenness exposure(P <0.001).Per 0.1-unit increase in NDVI and EVI under different buffers were associated with 7.0–8.9% and 8.7–11.5% decline in the odds of LBW,and7.9–10.1% and 9.8–12.9% decline in odds of TLBW,respectively.Quartile analysis of greenness exposure revealed that higher levels of greenness exposure were significantly associated with lower risks of LBW and TLBW(P for trend <0.001).Compared to the first quartile,pregnant women exposed to the highest quartile of greenness exposure had a 3.5-4.4% lower risk of LBW and TLBW.Evidently nonlinear relationships were identified between greenness exposure and LBW or TLBW(P non-linear <0.001),exhibiting approximately "L"-shaped exposure-response functions with slopes being steeper at low greenness levels.Subgroup analysis showed a significantly stronger beneficial effect of greenness in lowering the risk of LBW and TLBW among younger,less educated,and village-dwelling mothers.In 2015,a considerable number of 15800–19759 LBWs and 9213–11257 TLBWs could be avoided by achieving greenness targets of mean NDVI/EVI in Iran during 2013–2018,representing 17.7–21.3% of total LBWs and 22.7–26.5% of total TLBWs,respectively.Conclusions : 1.Greenness exposure during pregnancy was significantly associated with decreased risks of LBW and TLBW.2.Evidently nonlinear relationships were identified between greenness exposure and LBW or TLBW,exhibiting approximately "L"-shaped exposure-response functions.3.Significantly stronger beneficial effects of greenness in lowering the risk of LBW and TLBW among younger,less educated,and village-dwelling mothers.4.Increasing greenness may be an effective intervention measure to reduce the incidence of LBW in less developed countries.