Tropical cyclone exposure and risk of adverse birth outcomes in urban and rural areas of Georgia.

Tropical cyclones (TCs) are highly destructive weather disasters. Prior studies of TCs and birth outcomes often examined single storms or single TC characteristics (e.g. maximum wind speed) and rarely assessed urban/rural differences. To better understand TC impacts on perinatal health, we evaluated associations between multiple TC exposure metrics and several adverse birth outcomes and considered urban-rural variations. We conducted a population-based time series analysis of 2436 478 singleton births in Georgia from 2000-2018, in which individual-level state birth records were aggregated to the county-week level and linked to weekly, county-level TC data from the National Oceanic and Atmospheric Administration and the National Aeronautics and Space Administration. TC exposure metrics included maximum sustained wind speed (>17, 22, 25 m s-1), cumulative rainfall (>125, 150, 175 mm), storm proximity (<5, 10, 20 km), and flooding events (yes/no). Generalized linear models with a Poisson distribution were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for weekly rates of preterm birth (PTB, <37 weeks), low birthweight (LBW, <2500 g), small-for-gestational-age (SGA, <10th percentile), and proportion of male births. Winds >22 m s-1 were associated with higher risk of PTB (RR = 1.58 [95% CI: 1.27, 1.96]), LBW (RR = 1.77 [95%CI: 1.40, 2.23]), and SGA (RR = 1.38 [95%CI: 1.12, 1.70]). Rainfall >175 mm was associated with PTB (RR = 1.44 [95%CI: 1.08, 1.93]) and LBW (RR = 2.06 [95%CI: 1.50, 2.83]). Proximity <5 km was associated with PTB (RR = 1.41 [95%CI: 1.04, 1.90]) and LBW (RR = 2.11 [95%CI: 1.38, 3.23]). Flooding was associated with LBW (RR = 1.11 [95%CI: 1.03, 1.21]) and SGA (RR = 1.08 [95%CI: 1.01, 1.16]). Risk estimates were generally higher in rural versus metropolitan counties. Across multiple metrics, TC exposures were linked to increased PTB and fetal growth restriction, with stronger effects in rural counties. These findings bolster information on perinatal risks of TCs and inform more targeted disaster preparedness.