The Impact of Extreme Heat Exposure on Pregnant People and Neonates: A State of the Science Review

Reassessing 'good' medical practice and the climate crisis

In August 2023, the General Medical Council released the latest update of Good Medical Practice, which sets out the standards of patient care and professional behaviour to be expected of UK doctors. These updated guidelines offer some environmental considerations that previous standards did not include. This paper explores these latest additions to Good Medical Practice through the healthcare ethics lens of non-maleficence, beneficence, justice and autonomy, alongside trust and physician well-being, to make the case that the latest updates to Good Medical Practice do not go far enough in specifying the duties for doctors in responding to climate and ecological emergencies to be seen as ethically justifiable.The paper argues that given the health implications of the climate crisis and the harms associated with high-emission healthcare, as well as the co-benefits of climate action on health, there must be a stronger commitment from the medical regulator to ensure the groundwork is set for doctors to learn, understand and advocate for the importance and urgency of practicing sustainable healthcare. The case for this is strengthened by also examining the importance of maintaining public trust in the medical profession as advocates for public health, along with the notable societal and generational injustices that continue to deepen as the climate emergency escalates.The paper concludes by arguing that doctors can and should be a part of writing a new chapter for health in the climate era, but our standards for practice need to offer a strengthened starting point of consensus for what is expected of the medical profession for that to come to fruition and raise questions as to what doctors can and should do when they have questions over their own regulators' commitment to maintaining public health in relation to the climate and ecological crisis.

MiR- 223 alleviates the heat-stress-induced inhibition of cell proliferation by targeting PRDM1

BACKGROUND

Heat stress, exacerbated by global warming, has emerged as a significant concern for both the health of dairy cattle and the quality of milk production. In vitro investigations suggest that primary bovine mammary epithelial cells exhibit enhanced levels of programmed cell death when subjected to elevated ambient temperatures, potentially resulting in a reduction in the total number of mammary epithelial cells within the mammary gland, thereby partially elucidating the diminished milk yield in lactating cows under heat stress. In vivo, heat stress affects both milk synthesis and secretion by directly acting on mammary epithelial cells and by altering hormonal levels and metabolic pathways, which can lead to long-term effects on mammary growth. Future research should focus on elucidating the molecular mechanisms by which heat stress regulates mammary development. Previous studies have demonstrated that heat stress induction results in a significant downregulation of miR- 223 in MAC-T cells; therefore, miR- 223 may play a crucial role in the response to heat stress. Nevertheless, the mechanism by which miR- 223 confers resistance to heat stress in MAC-T remains unclear.

METHODS

Here, to investigate how miR- 223 regulates the proliferation of MAC-T cells, we performed a combination of miRNA- 223 overexpression and inhibition strategies. We transfected MAC-T cells with miR- 223 mimics or inhibitors and evaluated the impact on cell proliferation using CCK- 8 assay, EdU assay, and RT-qPCR. Additionally, MAC-T cells subjected to heat stress were used to investigate how miR- 223 and its target gene regulate cell proliferation under heat stress, either by promoting or alleviating the inhibition of cell proliferation, as assessed by EdU assay, CCK- 8 assay, and RT-qPCR.

RESULTS

In this study, we investigated the effects of heat stress on MAC-T cell proliferation and gene expression. Bioinformatics analysis identified PRDM1 as a key regulator of proliferation, and it was selected for further investigation. RT-qPCR validated the upregulation of PRDM1 under heat stress, confirming its role in regulating cell proliferation. The results revealed that miR- 223 mimic promoted cell proliferation, with PRDM1 identified as its target gene. Importantly, after heat stress, the miR- 223 mimic or the knockdown of PRDM1 in MAC-T was proven to partially reverse the inhibition of proliferation.

CONCLUSION

Consequently, the miR- 223 targeting PRDM1 might be important in alleviating heat-stress-induced inhibition of cell proliferation. This would potentially alleviate heat stress-induced damage to the mammary gland, thereby improving milk production in dairy cows.

Scoping review of climate drivers on maternal health: current evidence and clinical implications

Objective

To systematically review the literature on associations between climate drivers and health outcomes among pregnant people. This review fills a gap by synthesizing evidence for a clinician audience.

Data Sources

Systematic scoping review of articles published in PubMed and clinicaltrials.gov from January 2010 through December 2023.

Study Eligibility Criteria

Empirical studies published in English-language peer-reviewed journals, assessing associations between select climate drivers and adverse maternal and birth outcomes. The review included studies examining heat, storms, sea level rise, flooding, drought, wildfires, and other climate-related factors. Health outcomes included preterm birth, low birthweight, small for gestational age, gestational diabetes, pre-eclampsia/eclampsia, miscarriage/stillbirth and maternal mortality.

Study Appraisal and Synthesis Methods

The scoping review protocol was registered with the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY202410004, January 3, 2024) and conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Data were extracted by 2 authors; quality and risk of bias was assessed independently.

Results

Total of 966 references were screened; 16.35% (k=158) met inclusion criteria. The majority of studies (146/158; 92.4%) documented statistically significant and clinically meaningful associations between climate drivers and adverse perinatal health outcomes, including risk of preterm birth, low birthweight, and stillbirth as well as preeclampsia, gestational diabetes, miscarriage, and maternal death. Among the most durable findings: extreme heat exposure in early and late pregnancy were associated with increased risk of preterm birth and stillbirth. Driven in part by large (often population-based) studies and objective outcomes from surveillance data or medical record reviews, studies in this scoping review were evaluated as high quality (scoring 7-9 on the Newcastle-Ottawa Scale). Risk of bias was generally low.

Conclusions

Climate drivers are consistently associated with adverse health outcomes for pregnant people. Continuing education for clinicians, and clinician-patient communications should be expanded to address risks of climate change and extreme weather exposure, especially risks of extreme heat in late-pregnancy. Results from this review should inform multilevel interventions to address adverse health effects of climate during pregnancy as well as practice advisories, protocols, checklists, and clinical guidelines in obstetrics.

Mental health disparities among maternal populations following heatwave exposure in North Carolina (2011-2019): a matched analysis

Background

The increasing incidence of extreme heat due to climate change poses a significant threat to maternal mental health in the U.S. We examine the association of acute exposure to heatwaves with maternal mental health conditions in North Carolina from 2011 to 2019.

Methods

We incorporate a matched analysis design using NC Hospital Discharge Data to examine emergency department admissions for psychiatric conditions during the warm season (May to September), matching heatwave periods with non-heatwave unexposed periods at the zip code tabulation area (ZCTA) level. We stratify the sample to examine effect modification across the rural-urban continuum, physiographic regions, measurements of neighborhood racial and economic inequality, and individual-level sociodemographic factors (e.g., age, race/ethnicity, and insurance type).

Findings

Our sample of 324,928 emergency department visits by pregnant individuals has a mean age of 25.8 years (SD: 5.84), with 9.3% (n = 30,205) identifying as Hispanic. Relative risk (RR) estimates and 95% confidence intervals (CI) indicate significant increases in maternal mental health burdens following heatwave exposure. Acute heatwave periods were associated with a 13% higher risk of severe mental illness (RRSMI: 1.13, CI: 1.08-1.19, p: <0.0001), while prolonged exposure to moderate-intensity heatwaves was associated with 37% higher risk (RRSMI: 1.37, CI: 1.19-1.58, p: <0.001). Individual factors (e.g., advanced maternal age and insurance providers) and neighborhood-level characteristics, like low socioeconomic status, racialized and economic segregation, rurality, and physiographic region, further modified the risk of adverse maternal mental health outcomes.

Interpretation

Our results add to the growing evidence of the impact of extreme heat on maternal mental health, particularly among vulnerable subpopulations. Additionally, findings emphasize the influence of socioeconomic and environmental contexts on mental health responses to heatwave exposure.

Funding

This work was supported by the Faculty Early Career Development Program (CAREER) award (grant #2044839) from the National Science Foundation and the National Institute of Environmental Health Sciences (NIEHS) award (grant #5R03ES035170-02).

Balancing benefits and risks of exercise in pregnancy: a qualitative analysis of social media discussion

Exercise improves pregnancy outcomes, but few pregnant individuals meet physical activity guidelines. The main objective of this study was to explore the perception of exercise during pregnancy using posts and comments on Reddit, a large social media platform. Relevant user-generated posts and comments were identified on Reddit by searching systematically for a combination of keywords related to pregnancy and exercise. A dataset of 120 posts and 2892 comments was randomly selected for reflexive thematic analysis. Three themes relating to perceptions of benefits and risks to exercise in pregnancy and how they influence decision-making were generated: (1) perceived benefits of exercise: 'We all know that exercise is good for us'; (2) perceived risks of exercise: Exercise as 'off limits'; and (3) information seeking and decision-making: 'I'm kinda stumped on exercise'. While the benefits of exercise during pregnancy are well recognised among Reddit users, perceived risks significantly influence their decisions to start, continue, adjust or stop exercising. Healthcare providers play a crucial role in guiding these exercise choices, emphasising the need for them to provide evidence-based advice and support pregnant individuals in achieving optimal physical activity levels. Addressing misinformation and providing supportive counselling can help pregnant individuals navigate the complexities of exercise during this critical period.

Assessment of heat stress contributing factors in the indoor environment among vulnerable populations in Klang Valley using principal component analysis (PCA)

Rising global temperatures can lead to heat waves, which in turn can pose health risks to the community. However, a notable gap remains in highlighting the primary contributing factors that amplify heat-health risk among vulnerable populations. This study aims to evaluate the precedence of heat stress contributing factors in urban and rural vulnerable populations living in hot and humid tropical regions. A comparative cross-sectional study was conducted, involving 108 respondents from urban and rural areas in Klang Valley, Malaysia, using a face-to-face interview and a validated questionnaire. Data was analyzed using the principal component analysis, categorizing factors into exposure, sensitivity, and adaptive capacity indicators. In urban areas, five principal components (PCs) explained 64.3% of variability, with primary factors being sensitivity (health morbidity, medicine intake, increased age), adaptive capacity (outdoor occupation type, lack of ceiling, longer residency duration), and exposure (lower ceiling height, increased building age). In rural, five PCs explained 71.5% of variability, with primary factors being exposure (lack of ceiling, high thermal conductivity roof material, increased building age, shorter residency duration), sensitivity (health morbidity, medicine intake, increased age), and adaptive capacity (female, non-smoking, higher BMI). The order of heat-health vulnerability indicators was sensitivity > adaptive capacity > exposure for urban areas, and exposure > sensitivity > adaptive capacity for rural areas. This study demonstrated a different pattern of leading contributors to heat stress between urban and rural vulnerable populations.

Educating Pregnant Women About the Dangers of Extreme Heat and Air Pollution

Climate change poses a serious threat to the health and well-being of pregnant women and their developing fetuses. Certain populations are at greater risk of adverse outcomes from air pollution, a contributing factor to climate change. In addition, heightened exposure to extreme heat, a consequence of climate change, exacerbates the existing health care inequities in the United States. Nurses, midwives, and other health care clinicians are uniquely positioned to reduce the harmful effects of climate change by educating pregnant women and their families and advocating for systems and policies that can decelerate climate change. The purpose of this article is to provide resources for clinicians to use in educating pregnant women about the risks of extreme heat and air pollution, their potential effects on pregnancy and neonatal outcomes, and strategies to help mitigate risk. We conclude with implications for practice, opportunities for advocacy, and areas for future research.

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.

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.