Ambient temperature exposure and hypertensive disorders of pregnancy in Sweden
Abstract
Background: Hypertensive disorders of pregnancy (HDP) are major causes of maternal morbidity and mortality. Evidence suggests ambient temperature may influence HDP risk, but existing studies are limited by small samples, inconsistent methods, and unclear exposure windows. We examined associations between extreme temperature during pregnancy and HDP risk, and identified critical exposure windows.
Methods: We included pregnancies from the Swedish Pregnancy Register (2014–2024). Daily ERA5 air temperature data (0.25°×0.25°) were linked to residential addresses. Weekly mean temperature exposure was evaluated across gestational weeks 0–19, as HDP are defined after 20 weeks, and within consecutive four-week intervals to assess timing, particularly during the placentation period. Gestational hypertension and preeclampsia were identified using ICD-10 codes. Logistic regression with distributed lag non-linear models estimated associations with extreme heat and cold, adjusting for adjusting for key covariates.
Results: Among 1,069,892 pregnancies, 37,421 (3.5%) had gestational hypertension and 33,878 (3.2%) preeclampsia. Heat exposure during weeks 0–19 (95th vs 75th percentile; 18.4 °C vs 14.0 °C) was associated with lower odds of gestational hypertension (adjusted odds ratio [aOR] 0.85, 95% CI 0.76–0.95), particularly during weeks 4–15. Cold exposure (5th vs 25th percentile; −3.7 °C vs 2.1 °C) was associated with higher odds (aOR 1.07, 95% CI 1.01–1.14), mainly during weeks 16–19. No significant associations were found for preeclampsia (heat aOR 0.98, 95% CI 0.88–1.10; cold aOR 1.00, 95% CI 0.94–1.07).
Conclusions: Ambient temperature exposure during early pregnancy was differentially associated with gestational hypertension, with heat linked to lower odds and cold linked to higher odds. No associations were observed for progression to preeclampsia. Temperature alerts in antenatal care guide protective prenatal care measures during extreme weather.
Key messages: • Ambient heat and cold exposure during pregnancy are associated with gestational hypertension but not preeclampsia, with specific critical gestational windows identified.
• Findings support integrating temperature-related risk awareness into antenatal care to better protect pregnant individuals during extreme weather periods.
Related
- High ambient temperatures and hypertensive disorders of pregnancy: a systematic review
- Hypertension in People with Multiple Sclerosis: Epidemiology, Mechanisms, Hypertensive Disorders of Pregnancy, and Clinical Implications.
- Causal effects of physical activity and sedentary behaviors on hypertensive disorders of pregnancy: a two-sample Mendelian randomization study
- Effect of ambient temperature and thermal comfort indices on emergency visits for psychotic and mood disorders: a case-crossover study in a French suburban area
- County-Level Structural Racism and Racial Disparities in Hypertensive Disorders of Pregnancy in Georgia
BibTeX
@article{bao2026ambient,
title = {{Ambient temperature exposure and hypertensive disorders of pregnancy in Sweden}},
author = {M Bao and MM Brennan and F Nobile and P Ljungman and S Luchters and MF Chersich and O Stephansson and M Stafoggia and R Shraim and J De Bont},
journal = {The European Journal of Public Health},
year = {2026},
month = oct,
doi = {10.1093/eurpub/ckag169.951},
url = {https://doi.org/10.1093/eurpub/ckag169.951},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Ambient temperature exposure and hypertensive disorders of pregnancy in Sweden
AU - M Bao
AU - MM Brennan
AU - F Nobile
AU - P Ljungman
AU - S Luchters
AU - MF Chersich
AU - O Stephansson
AU - M Stafoggia
AU - R Shraim
AU - J De Bont
PY - 2026
DA - 2026/10/01
JO - The European Journal of Public Health
DO - 10.1093/eurpub/ckag169.951
UR - https://doi.org/10.1093/eurpub/ckag169.951
AB - Background: Hypertensive disorders of pregnancy (HDP) are major causes of maternal morbidity and mortality. Evidence suggests ambient temperature may influence HDP risk, but existing studies are limited by small samples, inconsistent methods, and unclear exposure windows. We examined associations between extreme temperature during pregnancy and HDP risk, and identified critical exposure windows. Methods: We included pregnancies from the Swedish Pregnancy Register (2014–2024). Daily ERA5 air temperature data (0.25°×0.25°) were linked to residential addresses. Weekly mean temperature exposure was evaluated across gestational weeks 0–19, as HDP are defined after 20 weeks, and within consecutive four-week intervals to assess timing, particularly during the placentation period. Gestational hypertension and preeclampsia were identified using ICD-10 codes. Logistic regression with distributed lag non-linear models estimated associations with extreme heat and cold, adjusting for adjusting for key covariates. Results: Among 1,069,892 pregnancies, 37,421 (3.5%) had gestational hypertension and 33,878 (3.2%) preeclampsia. Heat exposure during weeks 0–19 (95th vs 75th percentile; 18.4 °C vs 14.0 °C) was associated with lower odds of gestational hypertension (adjusted odds ratio [aOR] 0.85, 95% CI 0.76–0.95), particularly during weeks 4–15. Cold exposure (5th vs 25th percentile; −3.7 °C vs 2.1 °C) was associated with higher odds (aOR 1.07, 95% CI 1.01–1.14), mainly during weeks 16–19. No significant associations were found for preeclampsia (heat aOR 0.98, 95% CI 0.88–1.10; cold aOR 1.00, 95% CI 0.94–1.07). Conclusions: Ambient temperature exposure during early pregnancy was differentially associated with gestational hypertension, with heat linked to lower odds and cold linked to higher odds. No associations were observed for progression to preeclampsia. Temperature alerts in antenatal care guide protective prenatal care measures during extreme weather. Key messages: • Ambient heat and cold exposure during pregnancy are associated with gestational hypertension but not preeclampsia, with specific critical gestational windows identified. • Findings support integrating temperature-related risk awareness into antenatal care to better protect pregnant individuals during extreme weather periods.
SN - 1101-1262
SN - 1464-360X
ER -