Associations between high temperatures in pregnancy and risk of preterm birth, low birth weight, and stillbirths: systematic review and meta-analysis

Development, validation and reliability of scales and items for heat wave risk assessment of pregnant women

INTRODUCTION

The 1.2 °C rise of global ambient temperature since the pre-industrial era has led to an increase the intensity and frequency of heatwaves. Given the heightened vulnerability of pregnant women to heat stress, there is an urgent need for tools which accurately assess the knowledge, risk, and perception of pregnant woman toward heatwaves, enabling effective policy actions. In this research, we developed and validated tools to evaluate pregnant women's perceptions of heat wave risks and behaviors.

METHOD

We developed 50 items across seven constructs using the Health Belief Model, identified through a systematic literature review. The constructs comprised 8 Knowledge(K) items, 4 in Perceived Vulnerability (PV), 5 in Perceived Severity (PS), 6 in Perceived Benefit (PB), 4 in Perceived Barrier (PBa), 5 in Cue to Action(Cu) and 18 in Adaptation(A). Cognitive testing was performed with a separate group of pregnant women(n = 20). The tested tools were then administered to 120 pregnant women residing during the spring-summer 2023. Construct validation utilized exploratory factor analysis.

RESULTS

The Principal Axis Factoring Method was employed in the EFA with oblimin rotation for 51 items, considering communality > 0.20, and aiming to extract three factors. Across the three factors with Cronbach's alpha > 0.70, a total of 11 items were distributed. Factor 1 included Perceived Severity (PS1, PS2, PS3 and PS5); Factor 2 included Cue to Action (Cu1, Cu2, Cu3, and Cu4); and Factor 3 encompassed Perceived Vulnerability (PV1, PV2, PV4). Only two of the retained items had factor loadings > 0.50, namely PV4 and PS5. Consequently, the three constructs measuring Perceived Severity, Cues to Action, and Perceived Vulnerability using the HBM among pregnant women were deemed valid.

CONCLUSION

Our study has successfully validated a highly reliable tool which stands ready for application in assessing pregnant women's risk perception regarding heatwaves.

Health effects of selected environmental Exposomes Across the Life courSe in Indian populations using longitudinal cohort studies: GEOHealth HEALS Study protocol

INTRODUCTION

Air pollution presents a major public health threat to India, affecting more than three quarters of the country's population. In the current project, GEOHealth Health Effects of Selected Environmental Exposomes Across the Life CourSe-India, we aim to study the effect of environmental exposomes-fine particulate matter (PM2.5), nitrogen dioxide (NO2), ozone (O3) and extremes of temperature-on multiple health outcomes using a modified life course approach. The associated training grant aims to build capacity in India to address the unique environmental health problems.

METHODS AND ANALYSIS

The project aims to (A) Develop exposure assessments in seven cities, namely Delhi, Chennai, Sonipat, Vizag, Pune, Hyderabad and Bikaner, for: (1) A fine-scale spatiotemporal model for multiple pollutants (PM2.5, NO2, O3, temperature); (2) Combined ground monitoring and modelling for major chemical species of ambient PM2.5 at seven cities; and (3) Personal exposure assessment in a subsample from the six cities, except Pune, and (B) Conduct health association studies covering a range of chronic non-communicable diseases and their risk factors leveraging a unique approach using interdigitating cohorts. We have assembled existing pregnancy, child, adolescent, adult and older adult cohorts across India to explore health effects of exposomes using causal analyses. We propose to use Bayesian kernel machine regression to assess the effects of mixtures of all pollutants including species of PM2.5 on health while accounting for potential non-linearities and interactions between exposures. This builds on earlier work that constructed a fine spatiotemporal model for PM2.5 exposure to study health outcomes in two Indian cities.

ETHICS AND DISSEMINATION

Ethical clearance for conduct of the study was obtained from the Institutional Ethics Committee (IEC) of the Centre for Chronic Disease Control, and all the participating institutes and organisations. National-level permission was provided by the Indian Council of Medical Research. The research findings will be disseminated through peer-reviewed publications, policy briefs, print and social media, and communicating with the participating communities and stakeholders. Training of Indian scientists will build the capacity to undertake research on selected adverse environmental exposures on population health in India.

Maternal exposure to ambient temperature and birth defects in Brazil: a nationwide case-control study of over 11 million newborns

Maternal exposure to extreme ambient temperature during pregnancy has been proposed as a potential risk factor for birth defects. Comprehensive investigations on this association remain limited, particularly in low- and middle-income countries. This study aims to examine the association between ambient temperature exposure during pregnancy and the risk of birth defects in Brazil, contributing to the broader understanding of environmental influences on birth outcomes. Using a large dataset of over 11 million live birth records, we analyzed 12 categories of birth defects, encompassing a time frame from 2001 to 2018. Ambient temperature data were assigned at the municipality level. For the exposure assessment, we considered two biologically driven pregnancy stages by dividing the gestational period into two specific windows: the first trimester (from week 1 to week 12) and the second trimester (from week 13 to week 28). We employed a two-stage case-control design. In the first stage, we applied a conditional logistic regression model to estimate the odds ratio (OR) for specific birth defects and each of the five Brazilian regions (North, Northeast, Midwest, Southeast, and South). The model was adjusted for potential confounding variables, including PM2.5, relative humidity, and socioeconomic status. Temporal trends were addressed using time-stratified sampling. In the second stage, we used mixed-effects meta-analysis to pool region-specific estimates. Our analysis revealed a significant association between maternal exposure to higher ambient temperatures during the first trimester and an increased risk of specific birth defect categories, including those affecting the genital organs (OR = 1.08, 95% CI: 1.02; 1.14), digestive system (OR = 1.12, 95% CI: 1.06; 1.19); circulatory system (OR = 1.08, 95% CI: 1.01; 1.17); eyes, ears, face, and neck (OR = 1.08, 95% CI: 1.02; 1.15); benign neoplasms tumors (OR = 1.17, 95% CI: 1.03; 1.32), musculoskeletal system (OR = 1.03, 95% CI: 1.01; 1.05); and other congenital anomalies (OR = 1.22, 95% CI: 1.15; 1.29). The associations with respiratory system, nervous system, and chromosomal anomalies were null. These findings have significant implications for public health policies aimed at mitigating the impact of environmental factors on birth outcomes, both in Brazil and globally.

Integrating observational and modelled data to advance the understanding of heat stress effects on pregnant subsistence farmers in the gambia

Studies on the effect of heat stress on pregnant women are scarce, particularly in highly vulnerable populations. To support the risk assessment of pregnant subsistence farmers in the West Kiang district, The Gambia we conducted a study on the pathophysiological effects of extreme heat stress and assessed the applicability of heat stress indices. From ERA5 climate reanalysis we added location-specific modelled solar radiation to datasets of a previous observational cohort study involving on-site measurements of 92 women working in the heat. Associations between physiological and environmental variables were assessed through Pearson correlation coefficient analysis, mixed effect linear models with random intercepts per participant and confirmatory composite analysis. We found Pearson correlations between r-values of 0 and 0.54, as well as independent effects of environmental variables on skin- and tympanic temperature, but not on heart rate, within a confidence interval of 98%. Pregnant women experienced stronger pathophysiological effects from heat stress in their third rather than in their second trimester. Environmental heat stress significantly altered maternal heat strain, particularly under humid conditions above a 50% relative humidity threshold, demonstrating interactive effects. Based on our results, we recommend including heat stress indices (e.g. UTCI or WBGT) in local heat-health warning systems.

Health impact of urban green spaces: a systematic review of heat-related morbidity and mortality

OBJECTIVES

The objective of this review was to scrutinise the impact of urban green spaces on heat-related morbidity and mortality.

DESIGN

This systematic review was meticulously carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines DATA SOURCES: A comprehensive search was conducted across PubMed, Scopus and Google Scholar including studies from January 2000 to December 2022.

ELIGIBILITY CRITERIA

Studies that examined the influence of urban green spaces on heat-related morbidity and mortality, including randomised controlled trials, observational and modelling studies, were included.

DATA EXTRACTION AND SYNTHESIS

A total of 3301 publications were initially identified, out of which 12 studies met the inclusion criteria and were selected for analysis. The selected studies were predominantly from high-income and upper-middle-income nations (95%).

RESULTS

The research points towards a pattern where regions abundant in green spaces report lower rates of heat-related morbidity and mortality in contrast to those with sparse greenery. Additionally, urban vegetation appears to exert a positive influence on mental health and well-being, potentially aiding in offsetting the adverse health repercussions of high temperatures.

CONCLUSION

Urban green spaces play a vital role in mitigating heat-related health risks, offering a potential strategy for urban planning to address climate change and enhance public health. Additional research is required to thoroughly comprehend the magnitude of urban greenery's impact on heat-related morbidity and mortality, as well as its interplay with other variables, including air pollution, socioeconomic status, among others.

What tools are available to assess climate and environmental health impacts on perinatal families with an equity lens? A rapid review of the Canadian context

OBJECTIVES

This rapid review is designed to identify existing tools in the Canadian literature that assess the impacts of climate change on the health of perinatal families, particularly those who are equity-denied. Addressing the needs of equity-denied perinatal populations in the face of climate change is crucial to promoting equitable and inclusive perinatal care in Canada.

METHODS

Rapid review methodology was selected to provide evidence in a timely and cost-effective manner. PubMed/MEDLINE and gray literature (Google and Google Scholar) were searched for English and French papers published from 2013 onward. The original research question, focused on climate change and health, yielded very few relevant results. Therefore, the search was broadened to include environmental health. Garrity et al.'s (J Clin Epidemiol 130:13-22, 2021) nine-stage process was used to identify 11 relevant papers, extract the relevant data, and complete the narrative synthesis.

SYNTHESIS

This review revealed a significant lack of tools for comprehensively assessing climate-health impacts on perinatal families and equity-denied perinatal families. While Canadian perinatal health screenings focus on equity via indicators of several social determinants of health (e.g., income, social support), they largely omit climate considerations. Environmental health factors are more commonly included but remain minimal.

CONCLUSION

Climate-health screening tools are lacking yet needed in routine perinatal healthcare. Given the seriousness of climate change, urgent engagement of health systems and healthcare workers is essential to help mitigate and adapt to climate-health challenges, particularly for perinatal families experiencing health inequities.

Impact of Climate Change Education on Pregnant Women's Anxiety and Awareness

OBJECTIVE

To evaluate the impact of climate change education on pregnant women's climate change awareness and anxiety.

STUDY DESIGN

Quasi-experimental research with pre- and post-test design.

METHODS

This study was conducted among pregnant women who visited a tertiary maternity hospital between April and June 2023 to assess climate change awareness, perception, knowledge, behavioral and policy expectations, and anxiety before and after the introduction of climate change education. The first phase of the study was conducted by distributing a set of questions related to sociodemographics and completing the Climate Change Awareness Scale and the Climate Change Worry Scale, followed by climate change education where pregnant women were exposed to a brochure entitled "Pregnancy and Climate Change". After the intervention, pregnant women were assessed using the same questionnaire.

RESULTS

There was a significant decrease in pregnant women's anxiety regarding climate change (p < 0.001). Participants' awareness (p < 0.001), perception (p < 0.001), knowledge (p < 0.001), and policy expectations regarding climate change significantly increased (p < 0.001), while their anxiety levels decreased (p < 0.001).

CONCLUSION

The study suggests that climate change education may reduce climate change anxiety among pregnant women while also enhancing their awareness, and improving their perceptions, knowledge, behaviors, and policy expectations about climate change.

Strengthening Maternal and Infant Health Resilience Before Weather and Climate Disasters: Preparedness Resources from CDC's Division of Reproductive Health

This report describes opportunities to address emergency preparedness to incorporate the needs of pregnant and postpartum populations. This report briefly summarizes data on the impacts of weather and climate disasters on maternal and infant health and outlines opportunities for individuals, health care providers, and public health practitioners to increase capacity to prepare for these occurrences, which are becoming more frequent and costly. Specific resources from the U.S. Centers for Disease Control and Prevention's Division of Reproductive Health are shared to support individual preparedness, communication of disaster safety messages, and emergency preparedness planning capacity among health care providers and health departments.

Baicalin ameliorates heat stress-induced hepatic injury and intestinal microecology dysbiosis in late gestational mice

Heat stress (HS) disrupts intestinal microbiota, glycolipid metabolism, and hepatic mitochondrial function in late gestational mice. Baicalin (BAI), a Chinese herbal medicine known for its heat-clearing and anti-inflammatory properties, has shown promise in modulating intestinal microecology and mitigating inflammation in various organs. This study investigates whether baicalin attenuates HS-induced intestinal microbial dysbiosis and liver damage in pregnant mice during late gestation. Twenty-four pregnant mice were randomly assigned to four groups, including thermoneutral (TN) (24 ± 1 ℃), HS (35 ± 1 ℃), HS+BAI200 (oral gavaged with 200 mg/kg BW of BAI), and HS+BAI400 (oral gavaged with 400 mg/kg BW of BAI). 400 mg/kg BAI treatment markedly decreased the rectal temperature and increased fetal weight in HS pregnant mice. Furthermore, 400 mg/kg BAI administration effectively ameliorated HS-induced hepatic damage and lipid disorders, reducing HSP70, AST, and ALT levels while increasing TG concentration. Notably, it activated a network of genes involved in lipid synthesis, including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and oxidation, such as peroxisome proliferator-activated receptor alpha (PPARα), carnitine palmityl transferase 1 beta (CPT1β). Moreover, BAI intervention restored the intestinal morphology and barrier function, evidenced by increased intestinal villus height, the ratio of villus height to crypt depth, and colonic goblet cells numbers. 400 mg/kg of BAI treatment up-regulated the expression of tight junction proteins, such as claudin-1 and Zonula Occludens-1 (ZO-1), in the jejunum and ileum, counteracting HS-induced downregulation. High-throughput sequencing showed that BAI treatment altered cecal microbial composition, increasing the relative abundance of beneficial Bacteroidota and decreasing Deferribacterota, Turicibacter, and Akkermansia. Spearman's correlation analysis highlighted significant correlations between differential cecal microbiota and physiological indexes. In conclusion, BAI administration alleviated adverse impacts in heat-exposed mice during late gestation, improving maternal physiological parameters, and ameliorating hepatic damage with altered cecal microbial composition. The findings suggest that BAI may regulate the gut-liver axis by modulating intestinal morphology, microecology, and hepatic function.

A time-stratified, case-crossover study of heat exposure and perinatal mortality from 16 hospitals in sub-Saharan Africa

Growing evidence suggests that extreme heat events affect both pregnant women and their infants, but few studies are available from sub-Saharan Africa. Using data from 138,015 singleton births in 16 hospitals in Benin, Malawi, Tanzania and Uganda, we investigated the association between extreme heat and early perinatal deaths, including antepartum and intrapartum stillbirths, and deaths within 24 h after birth using a time-stratified case-crossover design. We observed an association between an increase from the 75th to the 99th percentile in mean temperature 1 week (lag 0-6 d) before childbirth and perinatal mortality (odds ratio (OR) = 1.34 (95% confidence interval (CI) 1.01-1.78)). The estimates for stillbirths were similarly positive, but CIs included unity: OR = 1.29 (95% CI 0.95-1.77) for all stillbirths, OR = 1.18 (95% CI 0.71-1.95) for antepartum stillbirths and OR = 1.64 (95% CI 0.74-3.63) for intrapartum stillbirths. The cumulative exposure-response curve suggested that the steepest slopes for heat for intrapartum stillbirths and associations were stronger during the hottest seasons. We conclude that short-term heat exposure may increase mortality risks, particularly for intrapartum stillbirths, raising the importance of improved intrapartum care.

Climate Change and Congenital Anomalies: A Population-Based Study of the Effect of Prolonged Extreme Heat Exposure on the Risk of Neural Tube Defects in France

BACKGROUND

Exposure to long-lasting extreme ambient temperatures in the periconceptional or early pregnancy period might increase the risk of neural tube defects (NTDs). We tested whether prolonged severe heat exposure as experienced during the 2003 extreme heatwave in France, affected the risk of NTDs.

METHODS

We retrieved NTD cases spanning from January 1994 to December 2018 from the Paris Registry of Congenital Malformations. The 2003 heatwave was characterized by the long duration and high intensity of nine consecutive days with temperatures ≥35°C. We classified monthly conceptions occurring in August 2003 as "exposed" to prolonged extreme heat around conception (i.e., periconceptional period). We assessed whether the risk of NTDs among cohorts exposed to the prolonged severe heatwave of 2003 in the periconceptional period differed from expected values using Poisson/negative binomial regression.

FINDINGS

We identified 1272 NTD cases from January 1994 to December 2018, yielding a monthly mean count of 4.24. Ten NTD cases occurred among births conceived in August 2003. The risk of NTD was increased in the cohort with periconceptional exposure to the August 2003 heatwave (relative risk = 2.14, 95% confidence interval: 1.46 to 3.13), compared to non-exposed cohorts. Sensitivity analyses excluding July and September months or restricting to summer months yielded consistent findings.

INTERPRETATION

Evidence from the "natural experiment" of an extreme climate event suggests an elevated risk of NTDs following exposure to prolonged extreme heat during the periconceptional period.

Beyond the incubator: applying a "one health" approach in the NICU

A "one health" approach recognises that human health, animal health and planetary health are closely interlinked and that a transdisciplinary approach is required to fully understand and maintain global health. While, by necessity, Neonatal Intensive Care has traditionally focused on the acutely unwell newborn, the avoidance of long-term harm is core to many management decisions. The COVID 19 pandemic and climate crisis have brought into sharp relief the importance of a "one health" approach as part of long-term health promotion in the holistic care of neonates, who may survive to experience the burden of future environmental crises. This narrative review seeks to integrate what we know about "one health" issues in the neonatal intensive care unit, notably antimicrobial resistance and climate change, and suggest "everyday changes" which can be utilised by practitioners to minimise the impact of neonatal intensive care on these global health issues. Many of the changes suggested not only represent important improvements for planetary health but are also core to good neonatal practice. IMPACT: Neonatal patients are likely to bear the burden of future environmental crises including pandemics and climate related disasters. While the focus of intensive care practitioners is acute illness, awareness of "one health" problems are important for our smallest patients as part of preventing long-term harm. High quality neonatal care can benefit both the planet and our patients.

Evaluating the Impact of Heat Stress on Placental Function: A Systematic Review

Ambient heat stress poses a significant threat to public health, with rising temperatures exacerbating the risks associated with pregnancy. This systematic review examined the associations between heat stress exposure and placental function, synthesizing methodologies from the existing literature to inform future research approaches. Analyzing 24 articles, it explores various study designs, temperature exposure parameters, pregnancy windows, and placental outcome variables. Findings across human and animal studies reveal diverse effects on placental weight, efficiency, blood flow, anatomy, gene expression, and steroid levels under heat stress conditions. While animal studies primarily utilize randomized controlled trials, human research relies on observational methodologies due to ethical constraints. Both demonstrate alterations in placental morphology and function, underscoring the importance of understanding these changes for maternal and fetal health. The review underscores the urgent need for further research, particularly in human populations, to elucidate mechanisms and develop interventions mitigating heat stress's adverse effects on placental health. Ultimately, this synthesis contributes to understanding the complex interplay between environmental factors and pregnancy outcomes, informing strategies for maternal and fetal well-being amidst climate change challenges.

Climate change and public health in California: A structured review of exposures, vulnerable populations, and adaptation measures

California faces several serious direct and indirect climate exposures that can adversely affect public health, some of which are already occurring. The public health burden now and in the future will depend on atmospheric greenhouse gas concentrations, underlying population vulnerabilities, and adaptation efforts. Here, we present a structured review of recent literature to examine the leading climate risks to public health in California, including extreme heat, extreme precipitation, wildfires, air pollution, and infectious diseases. Comparisons among different climate-health pathways are difficult due to inconsistencies in study design regarding spatial and temporal scales and health outcomes examined. We find, however, that the current public health burden likely affects thousands of Californians each year, depending on the exposure pathway and health outcome. Further, while more evidence exists for direct and indirect proximal health effects that are the focus of this review, distal pathways (e.g., impacts of drought on nutrition) are more uncertain but could add to this burden. We find that climate adaptation measures can provide significant health benefits, particularly in disadvantaged communities. We conclude with priority recommendations for future analyses and solution-driven policy actions.

Sex-specific effects of environmental temperature during gestation on fluctuating asymmetry in deciduous teeth

OBJECTIVES

External environmental heat exposure during gestation impacts the physiology of human development in utero, but evidence for these impacts has not yet been explored in dentition. We examined deciduous teeth for fluctuating asymmetry (FA), a measure of developmental instability, together with gestational environmental temperature data drawn from historical weather statistics.

MATERIALS AND METHODS

We measured dental casts from the longitudinal Burlington Growth Study, representing 172 participants (ages 3-6 years) with health records. FA was calculated from crown dimensions and intercuspal distances that develop during gestation. Multiple regression separated by sex (nfemale = 81) examined the effects of mean temperatures in each trimester, controlling for birth year.

RESULTS

In females, increased temperatures during the first trimester are significantly associated with an increase in FA (p = 0.03), specifically during the second and third prenatal months (p = 0.03). There is no relationship between temperature and FA for either sex in the second or third trimesters, when enamel is formed.

DISCUSSION

Dental instability may be sensitive to temperature in the first trimester in females during the scaffolding of crown shape and size in the earliest stages of tooth formation. Sexual dimorphism in growth investment strategies may explain the differences in results between males and females. Using enduring dental characteristics, these results advance our understanding of the effects of temperature on fetal physiology within a discrete period.

Impacts of heat exposure on pregnant women, fetuses and newborns: a systematic review and meta-analysis

Climate Change has wide-ranging and severe health impacts, especially for vulnerable groups. We systematically reviewed the literature (n=198 studies) on heat impacts on maternal, fetal, and neonatal health, conducted meta-analyses to quantify impacts, analysed periods of susceptibility, and graded certainty. Studies covered 66 countries and 23 outcomes. Our results showed increased odds of preterm birth of 1.04 (95%CI=1.03, 1.06) per 1°C increase in heat exposure and 1.26 (95%CI=1.08, 1.47) during heatwaves. Similar patterns were shown for stillbirths and congenital anomalies. Gestational diabetes mellitus odds increased by 28% (95%CI=1.05, 1.74) at higher exposures, whileodds of any obstetric complication increased by 25% (95%CI=1.09, 1.42) during heatwaves. Patterns in susceptibility windows vary by condition. The review demonstrated that escalating temperatures pose major threats to maternal and child health globally. Findings could inform research priorities and selection of heat-health indicators. Clearly more intensive action is needed to protect these vulnerable groups.

Understanding the physiological and biological response to ambient heat exposure in pregnancy: protocol for a systematic review and meta-analysis

INTRODUCTION

Climate change increases not only the frequency, intensity and duration of extreme heat events but also annual temperatures globally, resulting in many negative health effects, including harmful effects on pregnancy and pregnancy outcomes. As temperatures continue to increase precipitously, there is a growing need to understand the underlying biological pathways of this association. This systematic review will focus on maternal, placental and fetal changes that occur in pregnancy due to environmental heat stress exposure, in order to identify the evidence-based pathways that play a role in this association.

METHODS AND ANALYSIS

We will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We will search PubMed and Ovid Embase databases from inception using tested and validated search algorithms. Inclusion of any studies that involve pregnant women and have measured environmental heat stress exposure and either maternal, placental or fetal physiological or biochemical changes and are available in English. Modelling studies or those with only animals will be excluded. The risk of bias will be assessed using the Office of Health Assessment and Translation tool. Abstract screening, data extraction and risk of bias assessment will be conducted by two independent reviewers.Environmental parameters will be reported for each study and where possible these will be combined to calculate a heat stress indicator to allow comparison of exposure between studies. A narrative synthesis will be presented following standard guidelines. Where outcome measures have at least two levels of exposure, we will conduct a dose-response meta-analysis should there be at least three studies with the same outcome. A random effects meta-analysis will be conducted where at least three studies give the same outcome.

ETHICS AND DISSEMINATION

This systematic review and meta-analysis does not require ethical approval. Dissemination will be through peer-reviewed journal publication and presentation at international conferences/interest groups.

PROSPERO REGISTRATION NUMBER

CRD42024511153.

Heat exposure induced risks of preterm birth mediated by maternal hypertension

Heat exposure is associated with an increased risk of preterm birth (PTB), with previous work suggesting that maternal blood pressure may play a role in these associations. Here we conducted a cohort study of 197,080 singleton live births across 8 provinces in China from 2015 to 2018. The study first estimated the associations between heat exposure, maternal hypertension and clinical subtypes of PTB, and then quantified the role of maternal hypertension in heat and PTB using mediation analyses. We show that heat exposure (>85th, 90th and 95th percentiles of local temperature distributions) spanning from conception to the 20th gestational week was associated with a 15-21% increase in PTB, and a 20-22% increase in medically indicated PTB. Heat exposure is likely to increase the risk of maternal hypertension and elevated blood pressure. Maternal hypertension mediated 15.7% and 33.9% of the effects of heat exposure (>90th percentile) on PTB and medically indicated PTB, respectively. Based on this large-population study, we found that exposure to heat in early pregnancy can increase the risk of maternal hypertension, thereby affecting the incidence of PTB.

Temperature-related neonatal deaths attributable to climate change in 29 low- and middle-income countries

Exposure to high and low ambient temperatures increases the risk of neonatal mortality, but the contribution of climate change to temperature-related neonatal deaths is unknown. We use Demographic and Health Survey (DHS) data (n = 40,073) from 29 low- and middle-income countries to estimate the temperature-related burden of neonatal deaths between 2001 and 2019 that is attributable to climate change. We find that across all countries, 4.3% of neonatal deaths were associated with non-optimal temperatures. Climate change was responsible for 32% (range: 19-79%) of heat-related neonatal deaths, while reducing the respective cold-related burden by 30% (range: 10-63%). Climate change has impacted temperature-related neonatal deaths in all study countries, with most pronounced climate-induced losses from increased heat and gains from decreased cold observed in countries in sub-Saharan Africa. Future increases in global mean temperatures are expected to exacerbate the heat-related burden, which calls for ambitious mitigation and adaptation measures to safeguard the health of newborns.

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.

Climate change impacts on child and adolescent health and well-being: A narrative review

Background

Worldwide, the climate is changing and affecting the health and well-being of children in many ways. In this review, we provided an overview of how climate change-related events may affect child and adolescent health and well-being, including children's mental and physical health, nutrition, safety and security, learning opportunities, and family caregiving and connectedness.

Methods

In this narrative review, we highlighted and discussed peer-reviewed evidence from 2012-23, primarily from meta-analyses and systematic reviews. The search strategy used a large and varied number of search terms across three academic databases to identify relevant literature.

Results

There was consistent evidence across systematic reviews of impact on four themes. Climate-related events are associated with a) increases in posttraumatic stress and other mental health disorders in children and adolescents, b) increases in asthma, respiratory illnesses, diarrheal diseases and vector-borne diseases, c) increases in malnutrition and reduced growth and d) disruptions to responsive caregiving and family functioning, which can be linked to poor caregiver mental health, stress and loss of resources. Evidence of violence against children in climate-related disaster contexts is inconclusive. There is a lack of systematic review evidence on the associations between climate change and children's learning outcomes.

Conclusions

Systematic review evidence consistently points to negative associations between climate change and children's physical and mental health, well-being, and family functioning. Yet, much remains unknown about the causal pathways linking climate-change-related events and mental and physical health, responsive relationships and connectedness, nutrition, and learning in children and adolescents. This evidence is urgently needed so that adverse health and other impacts from climate change can be prevented or minimised through well-timed and appropriate action.

Environmental Exposures and Pediatric Cardiology: A Scientific Statement From the American Heart Association

Environmental toxicants and pollutants are causes of adverse health consequences, including well-established associations between environmental exposures and cardiovascular diseases. Environmental degradation is widely prevalent and has a long latency period between exposure and health outcome, potentially placing a large number of individuals at risk of these health consequences. Emerging evidence suggests that environmental exposures in early life may be key risk factors for cardiovascular conditions across the life span. Children are a particularly sensitive population for the detrimental effects of environmental toxicants and pollutants given the long-term cumulative effects of early-life exposures on health outcomes, including congenital heart disease, acquired cardiac diseases, and accumulation of cardiovascular disease risk factors. This scientific statement highlights representative examples for each of these cardiovascular disease subtypes and their determinants, focusing specifically on the associations between climate change and congenital heart disease, airborne particulate matter and Kawasaki disease, blood lead levels and blood pressure, and endocrine-disrupting chemicals with cardiometabolic risk factors. Because children are particularly dependent on their caregivers to address their health concerns, this scientific statement highlights the need for clinicians, research scientists, and policymakers to focus more on the linkages of environmental exposures with cardiovascular conditions in children and adolescents.

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

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.

Preterm and Early-Term Delivery After Heat Waves in 50 US Metropolitan Areas

Importance

Heat waves are increasing in frequency, intensity, and duration and may be acutely associated with pregnancy outcomes.

Objective

To examine changes in daily rates of preterm and early-term birth after heat waves in a 25-year nationwide study.

Design, Setting, and Participants

This cohort study of singleton births used birth records from 1993 to 2017 from the 50 most populous US metropolitan statistical areas (MSAs). The study included 53 million births, covering 52.8% of US births over the period. Data were analyzed between October 2022 and March 2023 at the National Center for Health Statistics.

Exposures

Daily temperature data from Daymet at 1-km2 resolution were averaged over each MSA using population weighting. Heat waves were defined in the 4 days (lag, 0-3 days) or 7 days (lag, 0-6 days) preceding birth.

Main Outcomes and Measures

Daily counts of preterm birth (28 to <37 weeks), early-term birth (37 to <39 weeks), and ongoing pregnancies in each gestational week on each day were enumerated in each MSA. Rate ratios for heat wave metrics were obtained from time-series models restricted to the warm season (May to September) adjusting for MSA, year, day of season, and day of week, and offset by pregnancies at risk.

Results

There were 53 154 816 eligible births in the 50 MSAs from 1993 to 2017; 2 153 609 preterm births and 5 795 313 early-term births occurring in the warm season were analyzed. A total of 30.0% of mothers were younger than 25 years, 53.8% were 25 to 34 years, and 16.3% were 35 years or older. Heat waves were positively associated with daily rates of preterm and early-term births, showing a dose-response association with heat wave duration and temperatures and stronger associations in the more acute 4-day window. After 4 consecutive days of mean temperatures exceeding the local 97.5th percentile, the rate ratio for preterm birth was 1.02 (95% CI, 1.00-1.03), and the rate ratio for early-term birth was 1.01 (95% CI, 1.01-1.02). For the same exposure, among those who were 29 years of age or younger, had a high school education or less, and belonged to a racial or ethnic minority group, the rate ratios were 1.04 (95% CI, 1.02-1.06) for preterm birth and 1.03 (95% CI, 1.02-1.05) for early-term birth. Results were robust to alternative heat wave definitions, excluding medically induced deliveries, and alternative statistical model specifications.

Conclusions and Relevance

In this cohort study, preterm and early-term birth rates increased after heat waves, particularly among socioeconomically disadvantaged subgroups. Extreme heat events have implications for perinatal health.

Application of the socioecological model to mitigate risks of heat illness

BACKGROUND

The socio-ecological model (SEM) is a widely used framework that can be applied to heat-related illness (HRI) in the context of multiple influencing factors that exist in society. Leaders and policymakers must intervene to mitigate the deleterious effects of climate change on those at risk.

PURPOSE

The purpose is to introduce the SEM as a framework to address the complex factors contributing to the impact of excess heat.

METHODS

Conceived through the SEM, the compounding and cumulative impact of excess heat resulting in HRI is operationalized.

DISCUSSION

The SEM provides a structure for understanding the complex nature of climate change and HRI and proposed interventions. The prevention of HRI is dependent on actions, related to practice, education, research, and advocacy across multiple levels of the SEM. The SEM has the potential to target HRI at all levels of society to reduce the harm of excess heat.

Ambient temperature and preterm birth: A case-crossover study

OBJECTIVE

To investigate the association between ambient temperature and preterm birth (PTB) and to estimate the population attributable fraction (PAF) of PTBs due to low and high temperatures.

DESIGN

Time-stratified case-crossover design.

SETTING

Japan (46 prefectures, excluding Okinawa), 2011-2020.

SAMPLE

214 050 PTBs registered in the Japan Perinatal Registry Network database among 1 908 168 singleton live births.

METHODS

A quasi-Poisson regression model with a distributed lag nonlinear model was employed to assess the associations between daily mean temperature and PTBs for a lag of 0-27 days in each prefecture. A random effects meta-analysis was conducted by combining effect estimates from the 46 prefectures to estimate pooled relative risks (RRs). The PAFs of the PTBs due to below or above the mean of the 46 median temperatures (16.0°C) were calculated.

MAIN OUTCOME MEASURES

Preterm singleton live births.

RESULTS

The association between daily mean temperature and PTB risk exhibited a U-shaped curve. The adjusted RRs were 1.15 (95% confidence interval [CI] 1.05-1.25) at the mean of the 1st percentiles (0.8°C) and 1.08 (95% CI 1.00-1.17) at the mean of the 99th percentiles (30.2°C) of 46 prefectures, with 16.0°C as the reference temperature. Approximately 2.3% (95% CI 0.6-4.0) of PTBs were attributable to low temperatures.

CONCLUSIONS

Both low and possibly high temperatures were associated with an increased risk of PTBs. These findings may help to inform preventive measures for pregnant women.

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.

It is time to explore the impact of length of gestation and fetal health on the human lifespan

A recently proposed principal law of lifespan (PLOSP) proposes to extend the whole human lifespan by elongating different life stages. As the preborn stage of a human being, gestation is the foundation for the healthy development of the human body. The antagonistic pleiotropy (AP) theory of aging states that there is a trade-off between early life fitness and late-life mortality. The question is whether slower development during the gestation period would be associated with a longer lifespan. Among all living creatures, the length of the gestation period is highly positively correlated to the length of the lifespan, although such a correlation is thought to be influenced by the body sizes of different species. While examining the relationship between lifespan length and body size within the same species, dogs exhibit a negative correlation between lifespans and body sizes, while there is no such correlation among domestic cats. For humans, most adverse gestational environments shorten the period of gestation, and their impacts are long-term. While many issues remain unsolved, various developmental features have been linked to the conditions during the gestation period. Given that the length of human pregnancies can vary randomly by as long as 5 weeks, it is worth investigating whether a slow steady healthy gestation over a longer period will be related to a longer and healthier lifespan. This article discusses the potential benefits, negative impacts, and challenges of the relative elongation of the gestation period.

Women, girls, and climate change: Human rights, vulnerabilities, and opportunities

Our world faces potentially catastrophic climate change that can damage human health in multiple ways. The impact of climate change is uneven, disproportionately affecting the lives and livelihoods of women and girls. This conceptual article compiles evidence for a model that argues that climate change has more detrimental consequences for women than men because of women's precarity (unequal power) and corporal (physical) vulnerability. Climate change challenges the human rights of women and girls, triggering displacement, interrupted education, food and water scarcity, economic instability, mental and physical health challenges, reproductive injustice, gender-based violence, exploitation and human trafficking. Women are effective and essential change agents; their empowerment can directly contravene or mitigate climate change and also break the links between climate change and its negative consequences for women and girls. Gender-sensitive responses to the effects of climate change are imperative. Women's empowerment will further human rights and achievement of the United Nations Sustainable Development Goals.

Heat stress and adverse pregnancy outcome: Prospective cohort study

OBJECTIVE

To explore the relationship between occupational heat exposure, physiological heat strain indicators and adverse outcomes in pregnant women.

DESIGN

Prospective cohort.

SETTING

Workplaces in Tamil Nadu, India.

SAMPLE

A cohort of 800 pregnant women engaged in moderate to heavy physical work in 2017-2019 and 2021-2022.

METHODS

Participants were recruited at between 8 and 14 weeks of gestation. Occupational heat exposure and heat strain indicators were captured each trimester. 'Heat exposed' was defined as heat stress exceeding the threshold limit value (TLV) for safe manual work (with maximum wet-bulb globe temperatures of 27.5°C for a heavy workload and 28.0°C for a moderate workload). Physiological heat strain indicators (HSIs) such as core body temperature (CBT) and urine specific gravity (USG) were measured before and after each shift. Heat-related health symptoms were captured using the modified HOTHAPS questionnaire.

MAIN OUTCOME MEASURES

The main outcome measures included (1) a composite measure of any adverse pregnancy outcome (APO) during pregnancy (including miscarriage, preterm birth, low birthweight, stillbirth, intrauterine growth restriction and birth defects), (2) a composite measure of adverse outcomes at birth (3) and miscarriage.

RESULTS

Of the 800 participants, 47.3% had high occupational heat exposure. A rise in CBT was recorded in 17.4% of exposed workers, and 29.6% of workers experienced moderate dehydration (USG ≥ 1.020). Heat-exposed women had a doubled risk of miscarriage (adjusted odds ratio, aOR 2.4; 95% confidence interval, 95% CI 1.0-5.7). High occupational heat exposure was associated with an increased risk of any adverse pregnancy and foetal outcome (aOR 2.3; 95% CI 1.4-3.8) and adverse outcome at birth (aOR 2.0; 95% CI 1.2-3.3).

CONCLUSIONS

High occupational heat exposure is associated with HSIs and adverse pregnancy outcomes in India.

Health of singleton neonates in Switzerland through time and crises: a cross-sectional study at the population level, 2007-2022

BACKGROUND

Being exposed to crises during pregnancy can affect maternal health through stress exposure, which can in return impact neonatal health. We investigated temporal trends in neonatal outcomes in Switzerland between 2007 and 2022 and their variations depending on exposure to the economic crisis of 2008, the flu pandemic of 2009, heatwaves (2015 and 2018) and the COVID-19 pandemic.

METHODS

Using individual cross-sectional data encompassing all births occurring in Switzerland at the monthly level (2007-2022), we analysed changes in birth weight and in the rates of preterm birth (PTB) and stillbirth through time with generalized additive models. We assessed whether the intensity or length of crisis exposure was associated with variations in these outcomes. Furthermore, we explored effects of exposure depending on trimesters of pregnancy.

RESULTS

Over 1.2 million singleton births were included in our analyses. While birth weight and the rate of stillbirth have remained stable since 2007, the rate of PTB has declined by one percentage point. Exposure to the crises led to different results, but effect sizes were overall small. Exposure to COVID-19, irrespective of the pregnancy trimester, was associated with a higher birth weight (+12 grams [95% confidence interval (CI) 5.5 to 17.9 grams]). Being exposed to COVID-19 during the last trimester was associated with an increased risk of stillbirth (odds ratio 1.24 [95%CI 1.02 to 1.50]). Exposure to the 2008 economic crisis during pregnancy was not associated with any changes in neonatal health outcomes, while heatwave effect was difficult to interpret.

CONCLUSION

Overall, maternal and neonatal health demonstrated resilience to the economic crisis and to the COVID-19 pandemic in a high-income country like Switzerland. However, the effect of exposure to the COVID-19 pandemic is dual, and the negative impact of maternal infection on pregnancy is well-documented. Stress exposure and economic constraint may also have had adverse effects among the most vulnerable subgroups of Switzerland. To investigate better the impact of heatwave exposure on neonatal health, weekly or daily-level data is needed, instead of monthly-level data.

Extreme Heat and Pregnancy: A Content Analysis of Heat Health Risk Communication by US Public Health Agencies

OBJECTIVES

Exposure to extreme heat events increases the risk for negative birth outcomes, including preterm birth. This study sought to determine the presence and content of web-based heat health information for pregnant people provided by federal, state, and local government public health websites.

METHODS

This website content analysis consisted of 17 federal, 50 state, and 21 city websites, and noted which of 25 recognized pregnancy heat health data elements were included. Data for the analysis were collected from March 12, 2022, through March 16, 2022.

RESULTS

The search identified 17 federal websites, 38 state websites, and 19 city websites with heat health information. Within these, only seven websites listed pregnant people as a vulnerable or at-risk population, and only six websites provided information related to heat health specifically for pregnancy. Of the 25 themes recognized as important for pregnancy risk during extreme heat exposure, only 11 were represented within these 6 websites.

CONCLUSION

The presence of web-based pregnancy heat health information is infrequent and limited in content. Boosting web-based publication of extreme heat and pregnancy risks could mitigate negative maternal and child health outcomes.

Effects of land cover and air pollution on the risk of preterm births

OBJECTIVE

To evaluate the association between gestational age and green areas, urban built areas, and the concentration of particulate matter 2.5 (PM2.5) in the city of São Paulo, analyzing the irregular distribution of these areas and pollution levels above the recommended level.

METHODS

The study population consisted of a cohort of live births from 2012, and data from the Live Birth Information System (Sinasc) of the city of São Paulo were used. Using satellite images and supervised classification, the distribution and quantity of green areas and built areas in the city of São Paulo was obtained, as well as the concentrations of PM2.5. Logistic regressions were used to obtain possible associations.

RESULTS

The results of the study show that a lower percentage of green areas is significantly associated with a higher chance of preterm births. A higher building density was positively associated with the odds ratio for preterm birth. We did not find any significant associations between air pollution (PM2.5) and preterm births.

CONCLUSIONS

The results of this study show that greener areas are less associated with preterm births when compared with less green areas.

Clinic- and laboratory-based measures of postural control in patellofemoral pain: A systematic review with meta-analysis and evidence gap map

BACKGROUND

Patellofemoral pain (PFP) is a prevalent musculoskeletal disorder associated with functional impairments. Although postural control is commonly assessed in people with PFP, there are inconsistent results regarding potential postural control deficits in this population.

RESEARCH QUESTION

This review aims to evaluate whether postural control is impaired in people with patellofemoral pain (PFP) and the effectiveness of interventions on postural control measures.

METHODS

We searched six databases from their inception to May 5, 2023. We included studies assessing clinic- or laboratory-based postural control measures in people with PFP compared to pain-free controls, and intervention studies with PFP populations. We assessed risk of bias using the Joanna Briggs Institute critical appraisal checklists and the Cochrane Risk of Bias 2 tool. We assessed the certainty of evidence using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. We used random-effects meta-analyses considering subgroups based on type of task, measure, and intervention.

RESULTS

Fifty-three studies were included. Very low certainty evidence indicated that people with PFP have shorter anterior (SMD = 0.53, 95 %CI:0.16,0.90), posteromedial (SMD = 0.54, 95 %CI:0.04,1.03) and posterolateral (SMD = 0.59, 95 %CI:0.11,1.07) reach distance, and worse composite score (SMD = 0.46, 95 %CI:0.22,0.70). Very low to moderate certainty evidence indicated that people with PFP have worse anterior-posterior and overall stability indexes during single-leg stance (SMD = -0.71, 95 %CI:-1.29,-0.14; SMD = -0.63, 95 %CI:-0.94,-0.32) and overall stability index during double-leg stance (SMD = -0.39, 95 %CI:-0.78,-0.00), but no differences in center of pressure area during stair ascent (SMD = 0.32, 95 %CI:-2.72, 3.36). Low certainty evidence indicated that kinesio taping improved anterior reach distance (SMD = -0.49, 95 %CI:-0.89,-0.09), while no significant differences were observed between pre- and post-intervention outcomes for conventional rehabilitation and rigid taping.

SIGNIFICANCE

Clinicians should use clinic- (star excursion or Y-balance tests) and laboratory-based (stability indexes) measures to identify impairments of postural control in people with PFP. Low certainty of evidence suggests short-term improvement in postural control with kinesio taping.

Short-term ambient temperature variations and incidence of preterm birth: A systematic review and meta-analysis

This study aimed to determine the short-term effects of ambient temperature variations exposures on the incidence of preterm birth (PTB) for each single lag day (lag0 to lag6) and cumulative lag days (lag0-1 to lag0-6) up to a week before birth. To find relevant publications, online databases, including Web of Science, PubMed, and Scopus were searched with appropriate keywords and Mesh terms from their inception to October 25, 2023. Overall, the number of 39 observational studies with 12.5 million pregnant women and 700.000 cases of PTB met our eligibility criteria. The associations of temperature variations with the incidence of PTB were investigated with two different meta-analyses, including the percentile meta-analysis (comparing different percentiles (P1 to P99) with a referent percentile (P50)), and the linear meta-analysis (per 5 °C increment of the temperature levels). For the percentile meta-analysis, we observed both extreme cold (P1, only lag 0) and heat (P95 and P99 with the highest risk at lag1 and lag0-6) exposures can be significantly associated with a higher risk of PTB. The pooled RR (95 % CI) per 5 °C increase in the temperature levels at lag0-6 was estimated as 1.038 (1.018, 1.058) for the overall analysis. Subgroup analysis based on the season shows a significant association in the warm season (RR = 1.082 and 95 % CI = 1.036, 1.128) at all lag days but not the cold season. For the single lag day, we observed the risk of PTB is the highest at lag1 and decreased with moving to lag6. In sum, we suppose there is a nearly V-shape non-linear association between air temperature levels and the incidence of PTB with the linear relationship for each unit increase (also decrease) in the temperature levels above (also below) moderate temperature limits. Future studies should investigate possible association of occupational heat and cold exposure during pregnancy on the incidence of adverse birth outcomes such as PTB.

Climate Change and Children's Health: Building a Healthy Future for Every Child

Observed changes in temperature, precipitation patterns, sea level, and extreme weather are destabilizing major determinants of human health. Children are at higher risk of climate-related health burdens than adults because of their unique behavior patterns; developing organ systems and physiology; greater exposure to air, food, and water contaminants per unit of body weight; and dependence on caregivers. Climate change harms children through numerous pathways, including air pollution, heat exposure, floods and hurricanes, food insecurity and nutrition, changing epidemiology of infections, and mental health harms. As the planet continues to warm, climate change's impacts will worsen, threatening to define the health and welfare of children at every stage of their lives. Children who already bear higher burden of disease because of living in low-wealth households and communities, lack of access to high quality education, and experiencing racism and other forms of unjust discrimination bear greater risk of suffering from climate change hazards. Climate change solutions, advanced through collaborative work of pediatricians, health systems, communities, corporations, and governments lead to immediate gains in child health and equity and build a foundation for generations of children to thrive. This technical report reviews the nature of climate change and its associated child health effects and supports the recommendations in the accompanying policy statement on climate change and children's health.

Indoor Temperature and Energy Insecurity: Implications for Prenatal Health Disparities in Extreme Heat Events

BACKGROUND

Extreme heat events are a major public health concern and are only expected to increase in intensity and severity as climate change continues to accelerate. Pregnant people are physiologically more vulnerable to the effects of extreme heat, and exposure can induce harm on both the pregnant person and the fetus.

OBJECTIVES

This commentary argues that there is a need for greater epidemiological research on indoor heat exposure and energy insecurity as potential drivers of maternal and child environmental health disparities.

DISCUSSION

While there is substantial evidence linking ambient (outdoor) high temperature to pregnancy-related outcomes, there is a lack of epidemiological evidence to date on pregnant people's exposure to high indoor temperature and adverse maternal and/or child health outcomes. Energy insecurity is disproportionately experienced by people with low incomes and/or people of color, and indoor temperature may play a role in shaping socioeconomic and racial/ethnic disparities in maternal and child health in the United States. Further research is needed to understand the relationship between indoor heat exposure, energy insecurity, and pregnancy outcomes in both parents and children and to inform potential policies and practices to enhance resilience and reduce maternal/child health disparities. https://doi.org/10.1289/EHP13706.

Health equity in pediatrics: Current concepts for the care of children in the 21st century (Dis Mon)

This is an analysis of important aspects of health equity in caring for children and adolescents written by a multidisciplinary team from different medical centers. In this discussion for clinicians, we look at definitions of pediatric health equity and the enormous impact of social determinants of health in this area. Factors involved with pediatric healthcare disparities that are considered include race, ethnicity, gender, age, poverty, socioeconomic status, LGBT status, living in rural communities, housing instability, food insecurity, access to transportation, availability of healthcare professionals, the status of education, and employment as well as immigration. Additional issues involved with health equity in pediatrics that are reviewed will include the impact of the COVID-19 pandemic, behavioral health concepts, and the negative health effects of climate change. Recommendations that are presented include reflection of one's own attitudes on as well as an understanding of these topics, consideration of the role of various healthcare providers (i.e., community health workers, peer health navigators, others), the impact of behavioral health integration, and the need for well-conceived curricula as well as multi-faceted training programs in pediatric health equity at the undergraduate and postgraduate medical education levels. Furthermore, ongoing research in pediatric health equity is needed to scrutinize current concepts and stimulate the development of ideas with an ever-greater positive influence on the health of our beloved children. Clinicians caring for children can serve as champions for the optimal health of children and their families; in addition, these healthcare professionals are uniquely positioned in their daily work to understand the drivers of health inequities and to be advocates for optimal health equity in the 21st century for all children and adolescents.

Maternal Exposure to Extreme Cold Events and Risk of Congenital Heart Defects: A Large Multicenter Study in China

Over the past decade, extreme temperature events have become more frequent and longer in duration. Previous studies on the association between extreme cold events (ECEs) and congenital heart defects (CHDs) are few and inconsistent. We conducted a national multicenter study in 1313 hospitals in 26 provinces in China and collected a total of 14 808 high CHD-risk participants from 2013 to 2021. We evaluated the ECEs experienced by each pregnant women during the embryonic period (3-8 weeks). The results indicated that ECEs experienced by pregnant women during the embryonic period were associated with the development of fetal CHD and were more strongly associated with some specific fetal CHD subtypes, such as pulmonary stenosis, pulmonary atresia, and tetralogy of Fallot. Of the CHD burden, 2.21% (95% CI: 1.43, 2.99%)-2.40% (95% CI: 1.26, 3.55%) of fetal CHD cases were attributable to ECEs during the embryonic period. Our findings emphasize the need to pay more attention to pregnant women whose embryonic period falls during the cold season to reduce cold spell detriments to newborns.

2024 Heart Disease and Stroke Statistics: A Report of US and Global Data From the American Heart Association

BACKGROUND

The American Heart Association (AHA), in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, nutrition, sleep, and obesity) and health factors (cholesterol, blood pressure, glucose control, and metabolic syndrome) that contribute to cardiovascular health. The AHA Heart Disease and Stroke Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, brain health, complications of pregnancy, kidney disease, congenital heart disease, rhythm disorders, sudden cardiac arrest, subclinical atherosclerosis, coronary heart disease, cardiomyopathy, heart failure, valvular disease, venous thromboembolism, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The AHA, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States and globally to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2024 AHA Statistical Update is the product of a full year's worth of effort in 2023 by dedicated volunteer clinicians and scientists, committed government professionals, and AHA staff members. The AHA strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional global data, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Recent Advances and Challenges in the Early Diagnosis and Treatment of Preterm Labor

Preterm birth (PTB) is the primary cause of neonatal mortality and long-term disabilities. The unknown mechanism behind PTB makes diagnosis difficult, yet early detection is necessary for controlling and averting related consequences. The primary focus of this work is to provide an overview of the known risk factors associated with preterm labor and the conventional and advanced procedures for early detection of PTB, including multi-omics and artificial intelligence/machine learning (AI/ML)- based approaches. It also discusses the principles of detecting various proteomic biomarkers based on lateral flow immunoassay and microfluidic chips, along with the commercially available point-of-care testing (POCT) devices and associated challenges. After briefing the therapeutic and preventive measures of PTB, this review summarizes with an outlook.

Reflections on a Century of Extreme Heat Event-Related Mortality Reporting in Canada

Climate change is causing more frequent and severe extreme heat events (EHEs) in Canada, resulting in significant loss of life. However, patterns across mortality reporting for historical EHEs have not been analyzed. To address this gap, we studied deaths in Canadian EHEs from 1936 to 2021, identifying trends and challenges. Our analysis revealed inconsistencies in mortality data, discrepancies between vulnerable populations identified, difficulties in determining the cause of death, and inconsistent reporting on social vulnerability indicators. We provide some observations that could help inform solutions to address the gaps and challenges, by moving toward more consistent and comprehensive reporting to ensure no population is overlooked. Accurately accounting for affected populations could help better target evidence-based interventions, and reduce vulnerability to extreme heat.

Spatial-temporal distribution of preterm birth in China, 1990-2020: A systematic review and modelling analysis

BACKGROUND

Little is known about the long-term trends of preterm birth rates in China and their geographic variation by province.

OBJECTIVES

To estimate the annual spatial-temporal distribution of preterm birth rates in China by province from 1990 to 2020.

DATA SOURCES

We searched PubMed, EMBASE, Web of Science, CNKI, WANFANG and VIP from January 1990 to September 2023.

STUDY SELECTION AND DATA EXTRACTION

Studies that provided data on preterm births in China after 1990 were included. Data were extracted following the Guidelines for Accurate and Transparent Health Estimates Reporting.

SYNTHESIS

We assessed the quality of each survey using a 9-point checklist. We estimated the annual preterm birth risk by province using Bayesian multilevel logistic regression models considering potential socioeconomic, environmental, and sanitary predictors.

RESULTS

Based on 634 survey data from 343 included studies, we found a gradual increase in the preterm birth risk in most provinces in China since 1990, with an average annual increase of 0.7% nationally. However, the preterm birth rates in Inner Mongolia, Hubei, and Fujian Province showed a decline, while those in Sichuan were quite stable since 1990. In 2020, the estimates of preterm birth rates ranged from 2.9% (95% Bayesian credible interval [BCI] 2.1, 3.8) in Inner Mongolia to 8.5% (95% BCI 6.6, 10.9) in Jiangxi, with the national estimate of 5.9% (95% BCI 4.3, 8.1). Specifically, some provinces were identified as high-risk provinces for either consistently high preterm birth rates (e.g. Jiangxi) or relatively large increases (e.g. Shanxi) since 1990.

CONCLUSIONS

This study provides annual information on the preterm birth risk in China since 1990 and identifies high-risk provinces to assist in targeted control and intervention for this health issue.

Protocol of an individual participant data meta-analysis to quantify the impact of high ambient temperatures on maternal and child health in Africa (HE2AT IPD)

INTRODUCTION

Globally, recognition is growing of the harmful impacts of high ambient temperatures (heat) on health in pregnant women and children. There remain, however, major evidence gaps on the extent to which heat increases the risks for adverse health outcomes, and how this varies between settings. Evidence gaps are especially large in Africa. We will conduct an individual participant data (IPD) meta-analysis to quantify the impacts of heat on maternal and child health in sub-Saharan Africa. A detailed understanding and quantification of linkages between heat, and maternal and child health is essential for developing solutions to this critical research and policy area.

METHODS AND ANALYSIS

We will use IPD from existing, large, longitudinal trial and cohort studies, on pregnant women and children from sub-Saharan Africa. We will systematically identify eligible studies through a mapping review, searching data repositories, and suggestions from experts. IPD will be acquired from data repositories, or through collaboration with data providers. Existing satellite imagery, climate reanalysis data, and station-based weather observations will be used to quantify weather and environmental exposures. IPD will be recoded and harmonised before being linked with climate, environmental, and socioeconomic data by location and time. Adopting a one-stage and two-stage meta-analysis method, analytical models such as time-to-event analysis, generalised additive models, and machine learning approaches will be employed to quantify associations between exposure to heat and adverse maternal and child health outcomes.

ETHICS AND DISSEMINATION

The study has been approved by ethics committees. There is minimal risk to study participants. Participant privacy is protected through the anonymisation of data for analysis, secure data transfer and restricted access. Findings will be disseminated through conferences, journal publications, related policy and research fora, and data may be shared in accordance with data sharing policies of the National Institutes of Health.

PROSPERO REGISTRATION NUMBER

CRD42022346068.

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.

The effects of heat stress on intrauterine development, reproductive function, and ovarian gene expression of F1 female mice as well as gene expression of F2 embryos†

Exposure to heat stress (HS) in utero was postulated to trigger an adaptive molecular response that can be transmitted to the next generation. Hence, this study assessed the impact of HS exposure at different stages of the gestational period of mice on the female F1 population and their offspring. Heat stress exposure (41°C and 65% relative humidity-RH) occurred during the first half (FP), the second half (SP), or the entire pregnancy (TP). A control group (C) was maintained in normothermic conditions (25°C, 45% RH) throughout the experiment. Heat stress had a significant negative effect on intrauterine development, mainly when HS exposure occurred in the first half of pregnancy (FP and TP groups). Postnatal growth of FP and TP mice was hindered until 4 weeks of age. The total number of follicles per ovary did not vary (P > 0.05) between the control and HS-exposed groups. Mean numbers of primordial follicles were lower (P < 0.05) in the sexually mature FP than those in SP and TP F1 females. However, the mean number of viable embryos after superovulation was lower (P < 0.05) in TP compared with C group. The expression of genes associated with physiological and cellular response to HS, autophagy, and apoptosis was significantly affected in the ovarian tissue of F1 females and F2 in vivo-derived blastocysts in all HS-exposed groups. In conclusion, exposure to HS during pregnancy compromised somatic development and reproductive parameters as well as altered gene expression profile that was then transmitted to the next generation of mice.