. Author manuscript; available in PMC: 2023 Mar 1.

Published in final edited form as: Environ Res. 2021 Nov 3;204(Pt C):112315. doi: 10.1016/j.envres.2021.112315

Table 3.

Associations between heat exposure (1°C increment) during last week of gestation and preterm birth stratified by urbanicity and greenness

HR (95% CI)	Urbanicity
HR (95% CI)	Urbanized Areas (UA)	Urban Cluster (UC)	Rural
Greenness
Low (<0.6)	1.061 (1.014, 1.110)	1.004 (0.994, 1.015)	1.014 (0.983, 1.046)
High (≥0.6)	1.016 (0.959, 1.077)	1.002 (0.988, 1.016)	1.018 (1.003, 1.033)

Note: Threshold for designating greenness as high or low based on the median of county-level average NDVI for all urbanicity categories.

Number of births by greenness category and urbanicity: UA and low greenness 15729, UA and high greenness 6535; UC and low greenness 247512, UC and high greenness 142114; Rural and low greenness 31063, Rural and high greenness 103488.

Models adjusted for maternal age, race/ethnicity, median annual household income, parity, infant sex, year of birth, maternal marital status, average dew point temp, region, and percentage of population with less than high school education.