Physiological and biological response to heat exposure in pregnancy: a systematic review and meta-analysis
File(s)
Published version
Author(s)
Bonell, Ana
Qureshi, Asma Abdul Malik
Flouris, Andreas D
Tsoutsoubi, Lydia
Sferruzzi-Perri, Amanda N
Type
Journal Article
Abstract
Background
Pregnant women are vulnerable to extreme heat due to physiological adaptations that alter thermoregulation and metabolism; however, the underlying physiological mechanisms remain inconclusive. This systematic review and meta-analysis synthesises the effects of environmental heat on maternal, placental, and fetal physiology, identifying key biophysiological pathways.
Methods
We searched PubMed and Embase from database inception to Jan 13, 2025, for studies of pregnant women exposed to heat. Observational and experimental studies conducted in laboratory or field settings were included. Grey literature was not included. Alterations in typical physiological functions resulting from heat exposure across maternal, placental, or fetal responses were considered outcomes. AB and AAMQ screened and extracted data independently. Random-effects meta-analyses and meta-regression were applied to examine associations between heat stress exposure parameters and physiological responses. The study was registered with PROSPERO (CRD42024511153).
Findings
The analysis included data from 201 906 pregnant women from 27 studies. Meta-analyses of physiological changes before and after heat exposure found mean increases of 38 beats per min (bpm) in maternal heart rate (95% CI 29·3–45·8; I2 91%; seven studies), 0·5°C in maternal core temperature (0·5–0·6; 84%; 12 studies), 1·9°C in maternal skin temperature (0·4–3·4; 99%; six studies), and 13 bpm in fetal heart rate (8·8–16·5; 78%; seven studies). On meta-regression, increased core temperature was associated with higher intensity activities and increased heat stress and inversely associated with gestational age. There were inconsistent changes in uterine and umbilical artery blood flow. However, a higher susceptibility to impaired uteroplacental blood flow was observed among pregnant women with hypertension or pre-eclampsia.
Interpretation
We found consistent acute physiological stress responses to heat exposure, with evidence that these responses were worse in pregnant women with pre-eclampsia. The paucity of available data highlights the need for more research to identify the underlying biological mechanisms that mediate pregnancy outcomes with high heat exposure.
Funding
Wellcome Trust.
Pregnant women are vulnerable to extreme heat due to physiological adaptations that alter thermoregulation and metabolism; however, the underlying physiological mechanisms remain inconclusive. This systematic review and meta-analysis synthesises the effects of environmental heat on maternal, placental, and fetal physiology, identifying key biophysiological pathways.
Methods
We searched PubMed and Embase from database inception to Jan 13, 2025, for studies of pregnant women exposed to heat. Observational and experimental studies conducted in laboratory or field settings were included. Grey literature was not included. Alterations in typical physiological functions resulting from heat exposure across maternal, placental, or fetal responses were considered outcomes. AB and AAMQ screened and extracted data independently. Random-effects meta-analyses and meta-regression were applied to examine associations between heat stress exposure parameters and physiological responses. The study was registered with PROSPERO (CRD42024511153).
Findings
The analysis included data from 201 906 pregnant women from 27 studies. Meta-analyses of physiological changes before and after heat exposure found mean increases of 38 beats per min (bpm) in maternal heart rate (95% CI 29·3–45·8; I2 91%; seven studies), 0·5°C in maternal core temperature (0·5–0·6; 84%; 12 studies), 1·9°C in maternal skin temperature (0·4–3·4; 99%; six studies), and 13 bpm in fetal heart rate (8·8–16·5; 78%; seven studies). On meta-regression, increased core temperature was associated with higher intensity activities and increased heat stress and inversely associated with gestational age. There were inconsistent changes in uterine and umbilical artery blood flow. However, a higher susceptibility to impaired uteroplacental blood flow was observed among pregnant women with hypertension or pre-eclampsia.
Interpretation
We found consistent acute physiological stress responses to heat exposure, with evidence that these responses were worse in pregnant women with pre-eclampsia. The paucity of available data highlights the need for more research to identify the underlying biological mechanisms that mediate pregnancy outcomes with high heat exposure.
Funding
Wellcome Trust.
Date Issued
2026-04-01
Date Acceptance
2026-01-21
Citation
The Lancet Planetary Health, 2026, 10 (4)
ISSN
2542-5196
Publisher
Elsevier
Start Page
101431
Journal / Book Title
The Lancet Planetary Health
Volume
10
Issue
4
Copyright Statement
© 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/42127955
Publication Status
Published
Coverage Spatial
Netherlands
Article Number
101431
Date Publish Online
2026-05-13