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. 2024 May 4;24(1):344.
doi: 10.1186/s12884-024-06512-0.

Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review

Nicholas Brink  1 , Darshnika P Lakhoo  2 , Ijeoma Solarin  2 , Gloria Maimela  2 , Peter von Dadelszen  3 , Shane Norris  4 , Matthew F Chersich  2 ; Climate and Heat-Health Study Group
Collaborators, Affiliations

Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review

Nicholas Brink et al. BMC Pregnancy Childbirth. .

Abstract

Background: Climate change, particularly global warming, is amongst the greatest threats to human health. While short-term effects of heat exposure in pregnancy, such as preterm birth, are well documented, long-term effects have received less attention. This review aims to systematically assess evidence on the long-term impacts on the foetus of heat exposure in utero.

Methods: A search was conducted in August 2019 and updated in April 2023 in MEDLINE(PubMed). We included studies on the relationship of environmental heat exposure during pregnancy and any long-term outcomes. Risk of bias was assessed using tools developed by the Joanna-Briggs Institute, and the evidence was appraised using the GRADE approach. Synthesis without Meta-Analysis (SWiM) guidelines were used.

Results: Eighteen thousand six hundred twenty one records were screened, with 29 studies included across six outcome groups. Studies were mostly conducted in high-income countries (n = 16/25), in cooler climates. All studies were observational, with 17 cohort, 5 case-control and 8 cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals ranged in age from neonates to adults, and the elderly. Increasing heat exposure during pregnancy was associated with decreased earnings and lower educational attainment (n = 4/6), as well as worsened cardiovascular (n = 3/6), respiratory (n = 3/3), psychiatric (n = 7/12) and anthropometric (n = 2/2) outcomes, possibly culminating in increased overall mortality (n = 2/3). The effect on female infants was greater than on males in 8 of 9 studies differentiating by sex. The quality of evidence was low in respiratory and longevity outcome groups to very low in all others.

Conclusions: Increasing heat exposure was associated with a multitude of detrimental outcomes across diverse body systems. The biological pathways involved are yet to be elucidated, but could include epigenetic and developmental perturbations, through interactions with the placenta and inflammation. This highlights the need for further research into the long-term effects of heat exposure, biological pathways, and possible adaptation strategies in studies, particularly in neglected regions. Heat exposure in-utero has the potential to compound existing health and social inequalities. Poor study design of the included studies constrains the conclusions of this review, with heterogenous exposure measures and outcomes rendering comparisons across contexts/studies difficult.

Trial registration: PROSPERO CRD 42019140136.

Keywords: Child health; Climate change; Epigenetics; Heat exposure; Long-term effects; Maternal health; Metabolic disease; Pregnancy; Socioeconomic impact.

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Conflict of interest statement

NB holds investments in companies involved in the production, distribution and use of fossil-fuels through managed funds and indices. MFC and DL hold investments in the fossil fuel industry through their pension fund, as per the policy of the Wits Health Consortium. The University of the Witwatersrand holds investments in the fossil fuel industry through their endowments and other financial reserves.

Figures

Fig. 1
Fig. 1
PRISMA flow diagram
Fig. 2
Fig. 2
Map showing countries where studies were conducted relative to mean annual temperature [21]
Fig. 3
Fig. 3
Map showing countries where studies were conducted relative to climate zones [16]
Fig. 4
Fig. 4
Figure showing vote counting across all outcome groups. No Effect = No direction of effect noted in study
Fig. 5
Fig. 5
Causal pathways
See this image and copyright information in PMC

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