Greenspace and Land Cover Diversity During Pregnancy in a Rural Region, and Associations With Birth Outcomes

Abstract

Beneficial effects on health outcomes have been observed from exposure to spaces with substantial green vegetation ("greenspace"). This includes studies of greenspace exposure on birth outcomes; however, these have been conducted largely in urban regions. We characterized residential exposure to greenspace and land cover diversity during pregnancy in rural northern New England, USA, investigating whether variation in greenspace or diversity related to newborn outcomes. Five landscape variables (greenspace land cover, land cover diversity, impervious surface area, tree canopy cover, and the Normalized Difference Vegetation Index) were aggregated within six circular zones of radii from 100 to 3,000 m around residential addresses, and distance to conservation land was measured, providing a total of 31 greenspace and diversity metrics. Four birth outcomes along with potentially confounding variables were obtained from 1,440 participants in the New Hampshire Birth Cohort Study. Higher greenspace land cover up to 3,000 m was associated with larger newborn head circumference, while impervious surface area (non-greenspace) had the opposite association. Further, birth length was positively associated with land cover diversity. These findings support beneficial health impacts of greenspace exposure observed in urban regions for certain health outcomes, such as newborn head circumference and length but not others such as birthweight and gestational age. Further our results indicate that larger radius buffer zones may be needed to characterize the rural landscape. Vegetation indices may not be interchangeable with other greenspace metrics such as land cover and impervious surface area in rural landscapes.

Figure 1

Map of the study region, showing NLCD land cover classes and participant residential locations (masked by randomization within 3‐digit zip code tabulation areas (ZCTAs); low‐population ZCTAs are merged with neighboring ZCTAs). Selected regionally significant cities and towns are indicated by yellow circles.

Figure 2

Six nested circular buffers around a sample location, with radii of 100, 250, 500, 1,000, 2,000, and 3,000 m. Basemap shows NLCD land cover (Homer et al., 2015) with shaded relief. Greenspace metrics for each buffer are listed in the table. Sample location is not an actual address from the study.

Figure 3

Two conceptual relationships between greenspace and health impact. (a) Health impact increases linearly over the entire range of greenspace fraction. (b) Health impact is highly responsive at low levels of greenspace but saturates when greenspace becomes widespread.