Extreme weather events and maternal health in low-income and middle-income countries: a scoping review.

BACKGROUND: Despite 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. OBJECTIVES: This 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 CRITERIA: Studies 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 EVIDENCE: We 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 METHODS: We 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. RESULTS: Fifteen 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. CONCLUSION: EWE 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 NUMBER: CRD42022352915.

Climate change, air pollution and maternal and newborn health: An overview of reviews of health outcomes.

Background: Climate change represents a fundamental threat to human health, with pregnant women and newborns being more susceptible than other populations. In this review, we aimed to describe the current landscape of available epidemiological evidence on key climate risks on maternal and newborn health (MNH). Methods: We sought to identify published systematic and scoping reviews investigating the impact of different climate hazards and air pollution on MNH outcomes. With this in mind, we developed a systematic search strategy based on the concepts of 'climate/air pollution hazards, 'maternal health,' and 'newborn health,' with restrictions to reviews published between 1 January 2010 and 6 February 2023, but without geographical or language restriction. Following full text screening and data extraction, we synthesised the results using narrative synthesis. Results: We found 79 reviews investigating the effects of climate hazards on MNH, mainly focussing on outdoor air pollution (n = 47, 59%), heat (n = 24, 30%), and flood/storm disasters (n = 7, 9%). Most were published after 2015 (n = 60, 76%). These reviews had consistent findings regarding the positive association of exposure to heat and to air pollution with adverse birth outcomes, particularly preterm birth. We found limited evidence for impacts of climate-related food and water security on MNH and did not identify any reviews on climate-sensitive infectious diseases and MNH. Conclusions: Climate change could undermine recent improvements in maternal and newborn health. Our review provides an overview of key climate risks to MNH. It could therefore be useful to the MNH community to better understand the MNH needs for each climate hazard and to strengthen discussions on evidence and research gaps and potential actions. Despite the lack of comprehensive evidence for some climate hazards and for many maternal, perinatal, and newborn outcomes, we observed repeated findings of the impact of heat and air pollutants on birth outcomes, particularly preterm birth. It is time for policy dialogue to follow to specifically design climate policy and actions to protect the needs of MNH.

A story of (in)coherence: climate adaptation for health in South African policies.

Climate adaptation strengthens and builds the resilience of health systems to future climate-related shocks. Adaptation strategies and policies are necessary tools for governments to address the long-term impacts of climate change and enable the health system to respond to current impacts such as extreme weather events. Since 2011 South Africa has national climate change policies and adaptation strategies, yet there is uncertainty about: how these policies and plans are executed; the extent to which health policies include adaptation; and the extent of policy coherence across sectors and governance levels. A policy document analysis was conducted to examine how South African climate change, development and health policy documents reflect the health adaptation response across national and Western Cape levels and to assess the extent of coherence across key health and environment sector policy documents, including elements to respond to health-related climate risks, that can support implementation. Our findings show that overall there is incoherence in South African climate adaptation within health policy documents. Although health adaptation measures are somewhat coherent in national level policies, there is limited coherence within Western Cape provincial level documents and limited discussion on climate adaptation, especially for health. Policies reflect formal decisions and should guide decision-makers and resourcing, and sectoral policies should move beyond mere acknowledgement of adaptation responses to a tailored plan of actions that are institutionalized and location and sector specific. Activities beyond documents also impact the coherence and implementation of climate adaptation for health in South Africa. Clear climate risk-specific documents for the health sector would provide a stronger plan to support the implementation of health adaptation and contribute to building health system's resilience.

Extreme heat, pregnancy and women's well-being in Burkina Faso: an ethnographical study.

Climate change is an increasing threat to the health of populations in Africa, with a shift in seasonal temperatures towards more extreme heat exposures. In Burkina Faso, like other countries in the Sahel, many women have little protection against exposure to high temperatures, either outside or inside the home or place of work. This paper investigates how women perceive the impacts of heat on their physical and mental health, in addition to their social relationships and economic activities. Qualitative methods (in-depth interviews and focus group discussions) were conducted with women, community representatives and healthcare professionals in two regions in Burkina Faso. A thematic analysis was used to explore the realities of participants' experiences and contextual perspectives in relation to heat. Our research shows extreme temperatures have a multifaceted impact on pregnant women, mothers and newborns. Extreme heat affects women's functionality and well-being. Heat undermines a woman's ability to care for themselves and their child and interferes negatively with breast feeding. Heat negatively affects their ability to work and to maintain harmonious relationships with their partners and families. Cultural practices such as a taboo on taking the baby outside before the 40th day may exacerbate some of the negative consequences of heat. Most women do not recognise heat stress symptoms and lack awareness of heat risks to health. There is a need to develop public health messages to reduce the impacts of heat on health in Burkina Faso. Programmes and policies are needed to strengthen the ability of health professionals to communicate with women about best practices in heat risk management.

Too hot to thrive: a qualitative inquiry of community perspectives on the effect of high ambient temperature on postpartum women and neonates in Kilifi, Kenya.

OBJECTIVE: To understand community perspectives on the effects of high ambient temperature on the health and wellbeing of neonates, and impacts on post-partum women and infant care in Kilifi. DESIGN: Qualitative study using key informant interviews, in-depth interviews and focus group discussions with pregnant and postpartum women (n = 22), mothers-in-law (n = 19), male spouses (n = 20), community health volunteers (CHVs) (n = 22) and stakeholders from health and government ministries (n = 16). SETTINGS: We conducted our research in Kilifi County in Kenya's Coast Province. The area is largely rural and during summer, air temperatures can reach 37˚C and rarely go below 23˚C. DATA ANALYSIS: Data were analyzed in NVivo 12, using both inductive and deductive approaches. RESULTS: High ambient temperature is perceived by community members to have direct and indirect health pathways in pregnancy and postpartum periods, including on the neonates. The direct impacts include injuries on the neonate's skin and in the mouth, leading to discomfort and affecting breastfeeding and sleeping. Participants described babies as "having no peace". Heat effects were perceived to be amplified by indoor air pollution and heat from indoor cooking fires. Community members believed that exclusive breastfeeding was not practical in conditions of extreme heat because it lowered breast milk production, which was, in turn, linked to a low scarcity of food and time spend by mothers away from their neonates performing household chores. Kangaroo Mother Care (KMC) was also negatively affected. Participants reported that postpartum women took longer to heal in the heat, were exhausted most of the time and tended not to attend postnatal care. CONCLUSIONS: High ambient temperatures affect postpartum women and their neonates through direct and indirect pathways. Discomfort makes it difficult for the mother to care for the baby. Multi-sectoral policies and programs are required to mitigate the negative impacts of high ambient temperatures on maternal and neonatal health in rural Kilifi and similar settings.

An expert review of environmental heat exposure and stillbirth in the face of climate change: Clinical implications and priority issues.

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.

Implementation of climate adaptation in the public health sector in Europe: qualitative thematic analysis.

BACKGROUND: Adaptation, to reduce the health impacts of climate change, is driven by political action, public support and events (extreme weather). National adaptation policies or strategies are limited in addressing human health risks and implementation of adaptation in the public health community is not well understood. AIM: To identify key issues in climate change adaptation implementation for public health in Europe. METHODS: Key informant interviews with decision-makers in international, national and local city governments in 19 European countries. Participants were recruited if a senior decision-maker working in public health, environmental health or climate adaptation. INTERVIEWS ADDRESSED: Barriers and levers for adaptation, policy alignment, networks and evidence needs. RESULTS: Thirty-two interviews were completed between June and October 2021 with 4 international, 5 national and 23 city/local government stakeholders. Respondents reported inadequate resources (funding, training and personnel) for health-adaptation implementation and the marginal role of health in adaptation policy. A clear mandate to act was key for implementation and resource allocation. Limited cross-departmental collaboration and poor understanding of the role of public health in climate policy were barriers to implementation. CONCLUSIONS: Across Europe, progress is varied in implementation of climate adaptation in public health planning. Providing appropriate resources, training, knowledge mobilization and supporting cross-departmental collaboration and multi-level governance will facilitate adaptation to protect human health.

Indicators to support local public health to reduce the impacts of heat on health.

Heat exposure presents a significant weather-related health risk in England and Wales, and is associated with acute impacts on mortality and adverse effects on a range of clinical conditions, as well as increased healthcare costs. Most heat-related health outcomes are preventable with health protection measures such as behavioural changes, individual cooling actions, and strategies implemented at the landscape level or related to improved urban infrastructure. We review current limitations in reporting systems and propose ten indicators to monitor changes in heat exposures, vulnerabilities, heat-health outcomes, and progress on adaptation actions. These indicators can primarily inform local area decision-making in managing risks across multiple sectors such as public health, adult and social care, housing, urban planning, and education. The indicators can be used alongside information on other vulnerabilities relevant for heat and health such as underlying morbidity or housing characteristics, to prioritise the most effective adaptation actions for those who need it the most.

Process and outputs from a community codesign workshop on reducing impact of heat exposure on pregnant and postpartum women and newborns in Kilifi, Kenya.

Background: Ambient 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. Methods: Following 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. Results: Twenty 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. Conclusion: Codesign 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.

Heatwaves, hospitals and health system resilience in England: a qualitative assessment of frontline perspectives from the hot summer of 2019.

OBJECTIVE: To critically assess the impacts of very hot weather on (i) frontline staff in hospitals in England and (ii) on healthcare delivery and patient safety. STUDY DESIGN: A qualitative study design using key informant semi-structured interviews, preinterview survey and thematic analysis. SETTING: England. PARTICIPANTS: 14 health professionals in the National Health Service (clinicians and non-clinicians, including facilities managers and emergency preparedness, resilience and response professionals). RESULTS: Hot weather in 2019 caused significant disruption to health services, facilities and equipment, staff and patient discomfort, and an acute increase in hospital admissions. Levels of awareness varied between clinical and non-clinical staff of the Heatwave Plan for England, Heat-Health Alerts and associated guidance. Response to heatwaves was affected by competing priorities and tensions including infection control, electric fan usage and patient safety. CONCLUSIONS: Healthcare delivery staff experience difficulty in managing heat risks in hospitals. Priority should be given to workforce development and strategic, long-term planning, prevention and investment to enable staff to prepare and respond, as well as to improve health system resilience to current and future heat-health risks. Further research with a wider, larger cohort is required to develop the evidence base on the impacts, including the costs of those impacts, and to assess the effectiveness and feasibility of interventions. Forming a national picture of health system resilience to heatwaves will support national adaptation planning for health, in addition to informing strategic prevention and effective emergency response.

Factors associated with older adults' perception of health risks of hot and cold weather event exposure: A scoping review.

Introduction: Hot and cold weather events are increasingly becoming a global burden resulting in premature and preventable morbidity and mortality, particularly in vulnerable groups such as older people and people with chronic health conditions. However, risk perception regarding weather is generally poor among vulnerable groups which often acts as a barrier to the uptake of critical health-protective behaviours. A more cohesive understanding of determinants of risk perception is needed to inform public health risk communication and behaviour change interventions that promote protective health behaviours. This scoping literature review aimed to understand factors influencing perception of personal health risks in vulnerable groups as a result of exposure to hot and cold weather events. Methods: A five-stage scoping review framework was followed. Searches were run across Medline, PsychInfo, Web of Science and EMBASE. Papers were included if they provided rationale for risk perceptions in vulnerable groups in indoor/domestic environments and focussed on samples from OECD countries. Results: In total, 13 out of 15,554 papers met the full inclusion criteria. The majority of papers focused on hot weather events: one study exclusively examined cold weather events and one study addressed both cold and hot weather events. Included papers focused on older adults aged 65+ years. The papers identified eight factors that were associated with older adults' personal health risk perception of hot and cold weather events: (1) Knowledge of the relationship between hot/cold weather and health risks, (2) presence of comorbidities, (3) age and self-identity, (4) perceived weather severity, (5) Beliefs associated with regional climate, (6) past experience with weather, (7) misconceptions of effectiveness of protective behaviours, and (8) external locus of control. Conclusions: Future research should explore risk communication methods by implementing the identified risk perception determinants from this review into health protection interventions targeting older adults. Further understanding is needed regarding risk perceptions in non-elderly vulnerable groups, for examples individuals with chronic diseases or disabilities.

How do high ambient temperatures affect infant feeding practices? A prospective cohort study of postpartum women in Bobo-Dioulasso, Burkina Faso.

OBJECTIVE: To examine the effects of high ambient temperature on infant feeding practices and childcare. DESIGN: Secondary analysis of quantitative data from a prospective cohort study. SETTING: Community-based interviews in the commune of Bobo-Dioulasso, Burkina Faso. Exclusive breastfeeding is not widely practised in Burkina Faso. PARTICIPANTS: 866 women (1:1 urban:rural) were interviewed over 12 months. Participants were interviewed at three time points: cohort entry (when between 20 weeks' gestation and 22 weeks' postpartum), three and nine months thereafter. Retention at nine-month follow-up was 90%. Our secondary analysis focused on postpartum women (n=857). EXPOSURE: Daily mean temperature (°C) measured at one weather station in Bobo-Dioulasso. Meteorological data were obtained from publicly available archives (TuTiempo.net). PRIMARY OUTCOME MEASURES: Self-reported time spent breastfeeding (minutes/day), exclusive breastfeeding of infants under 6 months (no fluids other than breast milk provided in past 24 hours), supplementary feeding of infants aged 6-12 months (any fluid other than breast milk provided in past 24 hours), time spent caring for children (minutes/day). RESULTS: The population experienced year-round high temperatures (daily mean temperature range=22.6°C-33.7°C). Breastfeeding decreased by 2.3 minutes/day (95% CI -4.6 to 0.04, p=0.05), and childcare increased by 0.6 minutes/day (0.06 to 1.2, p=0.03), per 1°C increase in same-day mean temperature. Temperature interacted with infant age to affect breastfeeding duration (p=0.02), with a stronger (negative) association between temperature and breastfeeding as infants aged (0-57 weeks). Odds of exclusive breastfeeding very young infants (0-3 months) tended to decrease as temperature increased (OR=0.88, 0.75 to 1.02, p=0.09). There was no association between temperature and exclusive breastfeeding at 3-6 months or supplementary feeding (6-12 months). CONCLUSIONS: Women spent considerably less time breastfeeding (~25 minutes/day) during the hottest, compared with coolest, times of the year. Climate change adaptation plans for health should include advice to breastfeeding mothers during periods of high temperature.

A systematic review of hot weather impacts on infant feeding practices in low-and middle-income countries.

Background: Increased rates of exclusive breastfeeding could significantly improve infant survival in low- and middle-income countries. There is a concern that increased hot weather due to climate change may increase rates of supplemental feeding due to infants requiring fluids, or the perception that infants are dehydrated. Objective: To understand how hot weather conditions may impact infant feeding practices by identifying and appraising evidence that exclusively breastfed infants can maintain hydration levels under hot weather conditions, and by examining available literature on infant feeding practices in hot weather. Methods: Systematic review of published studies that met inclusion criteria in MEDLINE, EMBASE, Global Health and Web of Science databases. The quality of included studies was appraised against predetermined criteria and relevant data extracted to produce a narrative synthesis of results. Results: Eighteen studies were identified. There is no evidence among studies of infant hydration that infants under the age of 6months require supplementary food or fluids in hot weather conditions. In some settings, healthcare providers and relatives continue to advise water supplementation in hot weather or during the warm seasons. Cultural practices, socio-economic status, and other locally specific factors also affect infant feeding practices and may be affected by weather and seasonal changes themselves. Conclusion: Interventions to discourage water/other fluid supplementation in breastfeeding infants below 6 months are needed, especially in low-middle income countries. Families and healthcare providers should be advised that exclusive breastfeeding (EBF) is recommended even in hot conditions.

The Effect of High and Low Ambient Temperature on Infant Health: A Systematic Review.

Children, and particularly infants, have physiological, anatomic, and social factors that increase vulnerability to temperature extremes. We performed a systematic review to explore the association between acute adverse infant outcomes (children 0-1 years) and exposure to high and low ambient temperatures. MEDLINE (Pubmed), Embase, CINAHL Plus, and Global Health were searched alongside the reference lists of key papers. We included published journal papers in English that assessed adverse infant outcomes related to short-term weather-related temperature exposure. Twenty-six studies met our inclusion criteria. Outcomes assessed included: infant mortality (n = 9), sudden infant death syndrome (n = 5), hospital visits or admissions (n = 5), infectious disease outcomes (n = 5), and neonatal conditions such as jaundice (n = 2). Higher temperatures were associated with increased risk of acute infant mortality, hospital admissions, and hand, foot, and mouth disease. Several studies identified low temperature impacts on infant mortality and episodes of respiratory disease. Findings on temperature risks for sudden infant death syndrome were inconsistent. Only five studies were conducted in low- or middle-income countries, and evidence on subpopulations and temperature-sensitive infectious diseases was limited. Public health measures are required to reduce the impacts of heat and cold on infant health.

How Climate Change May Threaten Progress in Neonatal Health in the African Region.

Climate change is likely to have wide-ranging impacts on maternal and neonatal health in Africa. Populations in low-resource settings already experience adverse impacts from weather extremes, a high burden of disease from environmental exposures, and limited access to high-quality clinical care. Climate change is already increasing local temperatures. Neonates are at high risk of heat stress and dehydration due to their unique metabolism, physiology, growth, and developmental characteristics. Infants in low-income settings may have little protection against extreme heat due to housing design and limited access to affordable space cooling. Climate change may increase risks to neonatal health from weather disasters, decreasing food security, and facilitating infectious disease transmission. Effective interventions to reduce risks from the heat include health education on heat risks for mothers, caregivers, and clinicians; nature-based solutions to reduce urban heat islands; space cooling in health facilities; and equitable improvements in housing quality and food systems. Reductions in greenhouse gas emissions are essential to reduce the long-term impacts of climate change that will further undermine global health strategies to reduce neonatal mortality.

Ambient temperature during pregnancy and risk of maternal hypertensive disorders: A time-to-event study in Johannesburg, South Africa.

Hypertensive disorders in pregnancy are a leading cause of maternal and perinatal mortality and morbidity. We evaluate the effects of ambient temperature on risk of maternal hypertensive disorders throughout pregnancy. We used birth register data for all singleton births (22-43 weeks' gestation) recorded at a tertiary-level hospital in Johannesburg, South Africa, between July 2017-June 2018. Time-to-event analysis was combined with distributed lag non-linear models to examine the effects of mean weekly temperature, from conception to birth, on risk of (i) high blood pressure, hypertension, or gestational hypertension, and (ii) pre-eclampsia, eclampsia, or HELLP (hemolysis, elevated liver enzymes, low platelets). Low and high temperatures were defined as the 5th and 95th percentiles of daily mean temperature, respectively. Of 7986 women included, 844 (10.6%) had a hypertensive disorder of which 432 (51.2%) had high blood pressure/hypertension/gestational hypertension and 412 (48.8%) had pre-eclampsia/eclampsia/HELLP. High temperature in early pregnancy was associated with an increased risk of pre-eclampsia/eclampsia/HELLP. High temperature (23 °C vs 18 °C) in the third and fourth weeks of pregnancy posed the greatest risk, with hazard ratios of 1.76 (95% CI 1.12-2.78) and 1.79 (95% CI 1.19-2.71), respectively. Whereas, high temperatures in mid-late pregnancy tended to protect against pre-eclampsia/eclampsia/HELLP. Low temperature (11°) during the third trimester (from 29 weeks' gestation) was associated with an increased risk of high blood pressure/hypertension/gestational hypertension, however the strength and statistical significance of low temperature effects were reduced with model adjustments. Our findings support the hypothesis that high temperatures in early pregnancy increase risk of severe hypertensive disorders, likely through an effect on placental development. This highlights the need for greater awareness around the impacts of moderately high temperatures in early pregnancy through targeted advice, and for increased monitoring of pregnant women who conceive during periods of hot weather.

Associations between ambient temperature and risk of preterm birth in Sweden: A comparison of analytical approaches.

BACKGROUND: Evidence indicates that high temperatures are a risk factor for preterm birth. Increasing heat exposures due to climate change are therefore a concern for pregnant women. However, the large heterogeneity of study designs and statistical methods across previous studies complicate interpretation and comparisons. We investigated associations of short-term exposure to high ambient temperature with preterm birth in Sweden, applying three complementary analytical approaches. METHODS: We included 560,615 singleton live births between 2014 and 2019, identified in the Swedish Pregnancy Register. We estimated weekly mean temperatures at 1-km2 spatial resolution using a spatiotemporal machine learning methodology, and assigned them at the residential addresses of the study participants. The main outcomes of the study were gestational age in weeks and subcategories of preterm birth (<37 weeks): extremely preterm birth (<28 weeks), very preterm birth (from week 28 to <32), and moderately preterm birth (from week 32 to<37). Case-crossover, quantile regression and time-to-event analyses were applied to estimate the effects of short-term exposure to increased ambient temperature during the week before birth on preterm births. Furthermore, distributed lag nonlinear models (DLNM) were applied to identify susceptibility windows of exposures throughout pregnancy in relation to preterm birth. RESULTS: A total of 1924 births were extremely preterm (0.4%), 2636 very preterm (0.5%), and 23,664 moderately preterm (4.2%). Consistent across all three analytical approaches (case-crossover, quantile regression and time-to-event analyses), higher ambient temperature (95th vs 50th percentile) demonstrated increased risk of extremely preterm birth, but associations did not reach statistical significance. In DLNM models, we observed no evidence to suggest an increased effect of high temperature on preterm birth risk. Even so, a suggested trend was observed in both the quantile regression and time-to-event analyses of a higher risk of extremely preterm birth with higher temperature during the last week before birth. CONCLUSIONS: In Sweden, with high quality data on exposure and outcome, a temperate climate and good quality ante-natal health care, we did not find an association between high ambient temperatures and preterm births. Results were consistent across three complementary analytical approaches.

Heatwave Mortality in Summer 2020 in England: An Observational Study.

High ambient temperatures pose a significant risk to health. This study investigates the heatwave mortality in the summer of 2020 during the SARS-CoV-2 coronavirus (COVID-19) pandemic and related countermeasures. The heatwaves in 2020 caused more deaths than have been reported since the Heatwave Plan for England was introduced in 2004. The total and cause-specific mortality in 2020 was compared to previous heatwave events in England. The findings will help inform summer preparedness and planning in future years as society learns to live with COVID-19. Heatwave excess mortality in 2020 was similar to deaths occurring at home, in hospitals, and in care homes in the 65+ years group, and was comparable to the increases in previous years (2016-2018). The third heatwave in 2020 caused significant mortality in the younger age group (0-64) which has not been observed in previous years. Significant excess mortality was observed for cardiovascular disease, respiratory disease, and Alzheimer's and Dementia across all three heatwaves in persons aged 65+ years. There was no evidence that the heatwaves affected the proportional increase of people dying at home and not seeking heat-related health care. The most significant spike in daily mortality in August 2020 was associated with a period of high night-time temperatures. The results provide additional evidence that contextual factors are important for managing heatwave risks, particularly the importance of overheating in dwellings. The findings also suggest more action is also needed to address the vulnerability in the community and in health care settings during the acute response phase of a heatwave.

Physiological mechanisms of the impact of heat during pregnancy and the clinical implications: review of the evidence from an expert group meeting.

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.

Maternal and newborn health risks of climate change: A call for awareness and global action.

Climate change represents one of the largest global health threats of the 21st century with immediate and long-term consequences for the most vulnerable populations, especially in the poorest countries with the least capacity to adapt to climate change. Pregnant women and newborns are increasingly being recognized as vulnerable populations in the context of climate change. The effects can be direct or indirect through heat stress, extreme weather events and air pollution, potentially impacting both the immediate and long-term health of pregnant women and newborns through a broad range of mechanisms. In 2008, the World Health Organization passed a resolution during the 61st World Health Assembly, recognizing the need for research to identify strategies and health-system strengthening to mitigate the effects of climate change on health. Climate adaptation plans need to consider vulnerable populations such as pregnant women and neonates and a broad multisectoral approach to improve overall resilience of societies.