Prenatal greenspace exposure and cord blood cortisol levels: A cross-sectional study in a middle-income country.

Exposure to greenspace has been associated with reduced stress; however, the available evidence on such an association for the fetus is still very scarce. We, for the first time, investigated the association between maternal greenspace exposure and the level of cortisol, a stress hormone, in the cord blood. Our study was based on a cohort of 150 pregnant women in Sabzevar, Iran (2018). We comprehensively assessed greenspace exposure for each participant through (i) residential surrounding greenspace (using two satellite-derived vegetation indices), (ii) residential proximity to green spaces, (iii) maternal visual access to greenspace, (iv) use of public and private green spaces, (v) having a private garden, and (vi) the number of plant pots at home. Linear regression models were developed to assess the association of each indicator of greenspace exposure with cord blood cortisol levels, controlled for the relevant covariates. We observed that a higher residential surrounding greenspace (100 m buffer), having a window with greenspace view, window greenspace coverage of more than 50%, frequently looking at greenspace through window, residential proximity to large green spaces, and more time spent in green spaces were associated with lower cortisol levels in the cord blood. The findings for residential surrounding greenspace at 300 m and 500 m buffers, residential proximity to any green space regardless of its size, having a private garden, and number of plant pots at home were not conclusive. While about one-third of the association between residential surrounding greenspace (100 m buffer) could be mediated through reduction in exposure to air pollution, we did not observe any strong evidence for such a mediatory role for the visual access to greenspace. The findings stratified for parental education and housing type showed mixed patterns. Our findings suggest that more greenspace exposure might reduce cortisol level in the cord blood.