# Temperature extremes and maternal health: differential risks of severe maternal morbidity during heatwaves and coldwaves in North Carolina

## TL;DR

Extreme temperatures during pregnancy, especially in older mothers and rural areas, increase the risk of severe maternal complications in North Carolina.

## Contribution

This study identifies differential risks of severe maternal morbidity during heatwaves and coldwaves across subpopulations in North Carolina.

## Key findings

- Heatwave and coldwave exposure during the last week of pregnancy increases the risk of severe maternal morbidity in advanced maternal age subgroups.
- Coldwave exposure elevates SMM risk in rural and western mountain regions of North Carolina.
- Hispanic mothers show increased SMM risk during both heatwaves and coldwaves.

## Abstract

Objective Climate change is increasingly recognized as a significant public health threat, particularly for vulnerable populations such as pregnant women. This study examines the association between heatwave and coldwave exposure and the risk of severe maternal morbidity (SMM) at delivery in North Carolina from 2011 to 2019. Methods We incorporate a matched analysis design using patient delivery data to identify disparities across the rural-urban continuum, measurements of neighborhood racial and economic inequality, geographic region, and sociodemographic groups (age, race/ethnicity, and insurance type). Results We found elevated risks of SMM associated with heatwave and coldwave exposures We observed an increased risk of severe maternal morbidity (SMM20) at delivery following exposure to heatwave (HW RR: 1.07, CI: 1.02 to 1.11) and coldwave (CW RR: 1.05, CI: 1.02 to 1.09) events during the last week of gestation in the advanced maternal age (> 35) subgroup. For coldwaves, the risk of SMM20 was elevated during the last week of gestation in both the western mountains (RR: 1.10, CI: 1.02 to 1.18) and rural (RR: 1.14, CI: 1.01 to 1.29) regions. Hispanic subgroups exhibited elevated SMM risks, particularly during heatwaves (lag0 to lag7, RR: 1.09, CI: 1.00 to 1.18) and coldwaves (lag0 to lag3, RR: 1.10, CI: 1.01 to 1.19; lag0 to lag7, RR: 1.04, CI: 1.00 to 1.07). Conclusion Our findings suggest that extreme temperature events exacerbate vulnerabilities in specific maternal subpopulations, underscoring the need to account for local context and population characteristics in maternal health assessments. Future research should continue to explore these associations and the role of additional environmental and social factors in SMM risk.

The online version contains supplementary material available at 10.1007/s00484-025-03079-z.