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Abstract Many populations experience high seasonal temperatures. Pregnant women are considered vulnerable to extreme heat because ambient heat exposure has been linked to pregnancy complications including preterm birth and low birthweight. The physiological mechanisms that underpin these associations are poorly understood. We reviewed the existing research evidence to clarify the mechanisms that lead to adverse pregnancy outcomes in order to inform public health actions. A multi-disciplinary expert group met to review the existing evidence base and formulate a consensus regarding the physiological mechanisms that mediate the effect of high ambient temperature on pregnancy. A literature search was conducted in advance of the meeting to identify existing hypotheses and develop a series of questions and themes for discussion. Numerous hypotheses have been generated based on animal models and limited observational studies. There is growing evidence that pregnant women are able to appropriately thermoregulate; however, when exposed to extreme heat, there are a number of processes that may occur which could harm the mother or fetus including a reduction in placental blood flow, dehydration, and an inflammatory response that may trigger preterm birth. There is a lack of substantial evidence regarding the processes that cause heat exposure to harm pregnant women. Research is urgently needed to identify what causes the adverse outcomes in pregnancy related to high ambient temperatures so that the impact of climate change on pregnant women can be mitigated.
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An expert review of environmental heat exposure and stillbirth in the face of climate change: Clinical implications and priority issues
Abstract Exposure to extreme heat in pregnancy increases the risk of stillbirth. Progress in reducing stillbirth rates has stalled, and populations are increasingly exposed to high temperatures and climate events that may further undermine health strategies. This narrative review summarises the current clinical and epidemiological evidence of the impact of maternal heat exposure on stillbirth risk. Out of 20 studies, 19 found an association between heat and stillbirth risk. Recent studies based in low‐ to middle‐income countries and tropical settings add to the existing literature to demonstrate that all populations are at risk. Additionally, both short‐term heat exposure and whole‐pregnancy heat exposure increase the risk of stillbirth. A definitive threshold of effect has not been identified, as most studies define exposure as above the 90th centile of the usual temperature for that population. Therefore, the association between heat and stillbirth has been found with exposures from as low as >12.64°C up to >46.4°C. The pathophysiological pathways by which maternal heat exposure may lead to stillbirth, based on human and animal studies, include both placental and embryonic or fetal impacts. Although evidence gaps remain and further research is needed to characterise these mechanistic pathways in more detail, preliminary evidence suggests epigenetic changes, alteration in imprinted genes, congenital abnormalities, reduction in placental blood flow, size and function all play a part. Finally, we explore this topic from a public health perspective; we discuss and evaluate the current public health guidance on minimising the risk of extreme heat in the community. There is limited pregnancy‐specific guidance within heatwave planning, and no evidence‐based interventions have been established to prevent poor pregnancy outcomes. We highlight priority research questions to move forward in the field and specifically note the urgent need for evidence‐based interventions that are sustainable.
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- Award ID(s):
- 2028598
- PAR ID:
- 10477058
- Publisher / Repository:
- BJOG
- Date Published:
- Journal Name:
- BJOG: An International Journal of Obstetrics & Gynaecology
- ISSN:
- 1470-0328
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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BackgroundDespite global efforts to improve maternal health and healthcare, women throughout the world endure poor health during pregnancy. Extreme weather events (EWE) disrupt infrastructure and access to medical services, however little is known about their impact on the health of women during pregnancy in resource-poor settings. ObjectivesThis review aims to examine the current literature on the impact of EWE on maternal health to identify the pathways between EWE and maternal health in low-income and middle-income countries to identify gaps. Eligibility criteriaStudies were eligible for inclusion if they were published before 15 December 2022 and the population of the studies included pregnant and postpartum women (defined at up to 6 weeks postpartum) who were living in low-income and middle-income countries. The exposure of the included study must be related to EWE and the result to maternal health outcomes. Sources of evidenceWe searched the literature using five databases, Medline, Global Health, Embase, Web of Science and CINAHL in December 2022. We assessed the results using predetermined criteria that defined the scope of the population, exposures and outcomes. In total, 15 studies were included. Charting methodsWe identified studies that fit the criteria and extracted key themes. We extracted population demographics and sampling methodologies, assessed the quality of the studies and conducted a narrative synthesis to summarise the key findings. ResultsFifteen studies met the inclusion criteria. The quantitative studies (n=4) and qualitative (n=11) demonstrated an association between EWE and malnutrition, mental health, mortality and access to maternal health services. ConclusionEWE negatively impact maternal health through various mechanisms including access to services, stress and mortality. The results have demonstrated concerning effects, but there is also limited evidence surrounding these broad topics in low-resource settings. Research is necessary to determine the mechanisms by which EWE affect maternal health. PROSPERO registration numberCRD42022352915.more » « less
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BackgroundAmbient heat exposure is increasing due to climate change and is known to affect the health of pregnant and postpartum women, and their newborns. Evidence for the effectiveness of interventions to prevent heat health outcomes in east Africa is limited. Codesigning and integrating local-indigenous and conventional knowledge is essential to develop effective adaptation to climate change. MethodsFollowing qualitative research on heat impacts in a community in Kilifi, Kenya, we conducted a two-day codesign workshop to inform a set of interventions to reduce the impact of heat exposure on maternal and neonatal health. Participants were drawn from a diverse group of purposively selected influencers, implementers, policy makers, service providers and community members. The key domains of focus for the discussion were: behavioral practices, health facilities and health system factors, home environment, water scarcity, and education and awareness. Following the discussions and group reflections, data was transcribed, coded and emerging intervention priorities ranked based on the likelihood of success, cost effectiveness, implementation feasibility, and sustainability. ResultsTwenty one participants participated in the codesign discussions. Accessibility to water supplies, social behavior-change campaigns, and education were ranked as the top three most sustainable and effective interventions with the highest likelihood of success. Prior planning and contextualizing local set-up, cross-cultural and religious practices and budget considerations are important in increasing the chances of a successful outcome in codesign. ConclusionCodesign of interventions on heat exposure with diverse groups of participants is feasible to identify and prioritize adaptation interventions. The codesign workshop was used as an opportunity to build capacity among facilitators and participants as well as to explore interventions to address the impact of heat exposure on pregnant and postpartum women, and newborns. We successfully used the codesign model in co-creating contextualized socio-culturally acceptable interventions to reduce the risk of heat on maternal and neonatal health in the context of climate change. Our interventions can be replicated in other similar areas of Africa and serve as a model for co-designing heat-health adaptation.more » « less
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Abstract Objective To assess whether exposure to high temperatures in pregnancy is associated with increased risk for preterm birth, low birth weight, and stillbirth. Design Systematic review and random effects meta-analysis. Data sources Medline and Web of Science searched up to September 2018, updated in August 2019. Eligibility criteria for selecting studies Clinical studies on associations between high environmental temperatures, and preterm birth, birth weight, and stillbirths. Results 14 880 records and 175 full text articles were screened. 70 studies were included, set in 27 countries, seven of which were countries with low or middle income. In 40 of 47 studies, preterm births were more common at higher than lower temperatures. Exposures were classified as heatwaves, 1°C increments, and temperature threshold cutoff points. In random effects meta-analysis, odds of a preterm birth rose 1.05-fold (95% confidence interval 1.03 to 1.07) per 1°C increase in temperature and 1.16-fold (1.10 to 1.23) during heatwaves. Higher temperature was associated with reduced birth weight in 18 of 28 studies, with considerable statistical heterogeneity. Eight studies on stillbirths all showed associations between temperature and stillbirth, with stillbirths increasing 1.05-fold (1.01 to 1.08) per 1°C rise in temperature. Associations between temperature and outcomes were largest among women in lower socioeconomic groups and at age extremes. The multiple temperature metrics and lag analyses limited comparison between studies and settings. Conclusions Although summary effect sizes are relatively small, heat exposures are common and the outcomes are important determinants of population health. Linkages between socioeconomic status and study outcomes suggest that risks might be largest in low and middle income countries. Temperature rises with global warming could have major implications for child health. Systematic review registration PROSPERO CRD 42019140136 and CRD 42018118113.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/1471-0528.17622
