Stillbirth Risk and Spatial Variation in Excess Death Rates During the 1918–1920 Influenza Pandemic in Arizona, USA

A large body of epidemiologic research has concentrated on the 1918 influenza pandemic, but more work is needed to understand spatial variation in pandemic mortality and pandemic impact on natality and stillbirths. We collected and analyzed 35,151 death records from Arizona for 1915–1921 and 21,334 birth records from Maricopa county, for 1915–1925. We estimated stillbirth risk and excess death rates and assessed the temporal association between pandemic-related excess mortality and stillbirths at different lags. There was a significant difference in stillbirth risk in the pandemic vs. post-pandemic periods (risk ratio = 1.96, P < 0.05). Pregnant women aged 20–39 years had the highest stillbirth risk during the pandemic. We found a significant trough in live births 10 and 11 months after the peak in excess deaths for males (r_db(10) = −0.26) and females (r_db(11) = −0.24). Moreover, northern counties with higher Native American population densities exhibited higher excess mortality rates, suggesting a link between ethnic and/or socio-demographic factors and risk of pandemic death. The relationship between stillbirth and pandemic mortality risk should be further studied at different spatial scales and in different ethnic groups.