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Abstract Many populations experience high seasonal temperatures. Pregnant women are considered vulnerable to extreme heat because ambient heat exposure has been linked to pregnancy complications including preterm birth and low birthweight. The physiological mechanisms that underpin these associations are poorly understood. We reviewed the existing research evidence to clarify the mechanisms that lead to adverse pregnancy outcomes in order to inform public health actions. A multi-disciplinary expert group met to review the existing evidence base and formulate a consensus regarding the physiological mechanisms that mediate the effect of high ambient temperature on pregnancy. A literature search was conducted in advance of the meeting to identify existing hypotheses and develop a series of questions and themes for discussion. Numerous hypotheses have been generated based on animal models and limited observational studies. There is growing evidence that pregnant women are able to appropriately thermoregulate; however, when exposed to extreme heat, there are a number of processes that may occur which could harm the mother or fetus including a reduction in placental blood flow, dehydration, and an inflammatory response that may trigger preterm birth. There is a lack of substantial evidence regarding the processes that cause heat exposure to harm pregnant women. Research is urgently needed to identify what causes the adverse outcomes in pregnancy related to high ambient temperatures so that the impact of climate change on pregnant women can be mitigated.
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An expert review of environmental heat exposure and stillbirth in the face of climate change: Clinical implications and priority issues
Abstract Exposure to extreme heat in pregnancy increases the risk of stillbirth. Progress in reducing stillbirth rates has stalled, and populations are increasingly exposed to high temperatures and climate events that may further undermine health strategies. This narrative review summarises the current clinical and epidemiological evidence of the impact of maternal heat exposure on stillbirth risk. Out of 20 studies, 19 found an association between heat and stillbirth risk. Recent studies based in low‐ to middle‐income countries and tropical settings add to the existing literature to demonstrate that all populations are at risk. Additionally, both short‐term heat exposure and whole‐pregnancy heat exposure increase the risk of stillbirth. A definitive threshold of effect has not been identified, as most studies define exposure as above the 90th centile of the usual temperature for that population. Therefore, the association between heat and stillbirth has been found with exposures from as low as >12.64°C up to >46.4°C. The pathophysiological pathways by which maternal heat exposure may lead to stillbirth, based on human and animal studies, include both placental and embryonic or fetal impacts. Although evidence gaps remain and further research is needed to characterise these mechanistic pathways in more detail, preliminary evidence suggests epigenetic changes, alteration in imprinted genes, congenital abnormalities, reduction in placental blood flow, size and function all play a part. Finally, we explore this topic from a public health perspective; we discuss and evaluate the current public health guidance on minimising the risk of extreme heat in the community. There is limited pregnancy‐specific guidance within heatwave planning, and no evidence‐based interventions have been established to prevent poor pregnancy outcomes. We highlight priority research questions to move forward in the field and specifically note the urgent need for evidence‐based interventions that are sustainable.
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- Award ID(s):
- 2028598
- PAR ID:
- 10477058
- Publisher / Repository:
- BJOG
- Date Published:
- Journal Name:
- BJOG: An International Journal of Obstetrics & Gynaecology
- ISSN:
- 1470-0328
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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BackgroundDespite global efforts to improve maternal health and healthcare, women throughout the world endure poor health during pregnancy. Extreme weather events (EWE) disrupt infrastructure and access to medical services, however little is known about their impact on the health of women during pregnancy in resource-poor settings. ObjectivesThis review aims to examine the current literature on the impact of EWE on maternal health to identify the pathways between EWE and maternal health in low-income and middle-income countries to identify gaps. Eligibility criteriaStudies were eligible for inclusion if they were published before 15 December 2022 and the population of the studies included pregnant and postpartum women (defined at up to 6 weeks postpartum) who were living in low-income and middle-income countries. The exposure of the included study must be related to EWE and the result to maternal health outcomes. Sources of evidenceWe searched the literature using five databases, Medline, Global Health, Embase, Web of Science and CINAHL in December 2022. We assessed the results using predetermined criteria that defined the scope of the population, exposures and outcomes. In total, 15 studies were included. Charting methodsWe identified studies that fit the criteria and extracted key themes. We extracted population demographics and sampling methodologies, assessed the quality of the studies and conducted a narrative synthesis to summarise the key findings. ResultsFifteen studies met the inclusion criteria. The quantitative studies (n=4) and qualitative (n=11) demonstrated an association between EWE and malnutrition, mental health, mortality and access to maternal health services. ConclusionEWE negatively impact maternal health through various mechanisms including access to services, stress and mortality. The results have demonstrated concerning effects, but there is also limited evidence surrounding these broad topics in low-resource settings. Research is necessary to determine the mechanisms by which EWE affect maternal health. PROSPERO registration numberCRD42022352915.more » « less
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BackgroundAmbient heat exposure is increasing due to climate change and is known to affect the health of pregnant and postpartum women, and their newborns. Evidence for the effectiveness of interventions to prevent heat health outcomes in east Africa is limited. Codesigning and integrating local-indigenous and conventional knowledge is essential to develop effective adaptation to climate change. MethodsFollowing qualitative research on heat impacts in a community in Kilifi, Kenya, we conducted a two-day codesign workshop to inform a set of interventions to reduce the impact of heat exposure on maternal and neonatal health. Participants were drawn from a diverse group of purposively selected influencers, implementers, policy makers, service providers and community members. The key domains of focus for the discussion were: behavioral practices, health facilities and health system factors, home environment, water scarcity, and education and awareness. Following the discussions and group reflections, data was transcribed, coded and emerging intervention priorities ranked based on the likelihood of success, cost effectiveness, implementation feasibility, and sustainability. ResultsTwenty one participants participated in the codesign discussions. Accessibility to water supplies, social behavior-change campaigns, and education were ranked as the top three most sustainable and effective interventions with the highest likelihood of success. Prior planning and contextualizing local set-up, cross-cultural and religious practices and budget considerations are important in increasing the chances of a successful outcome in codesign. ConclusionCodesign of interventions on heat exposure with diverse groups of participants is feasible to identify and prioritize adaptation interventions. The codesign workshop was used as an opportunity to build capacity among facilitators and participants as well as to explore interventions to address the impact of heat exposure on pregnant and postpartum women, and newborns. We successfully used the codesign model in co-creating contextualized socio-culturally acceptable interventions to reduce the risk of heat on maternal and neonatal health in the context of climate change. Our interventions can be replicated in other similar areas of Africa and serve as a model for co-designing heat-health adaptation.more » « less
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Abstract STUDY QUESTION Do daughters of older mothers have lower fecundability? SUMMARY ANSWER In this cohort study of North American pregnancy planners, there was virtually no association between maternal age ≥35 years and daughters’ fecundability. WHAT IS KNOWN ALREADY Despite suggestive evidence that daughters of older mothers may have lower fertility, only three retrospective studies have examined the association between maternal age and daughter’s fecundability. STUDY DESIGN, SIZE, DURATION Prospective cohort study of 6689 pregnancy planners enrolled between March 2016 and January 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS Pregnancy Study Online (PRESTO) is an ongoing pre-conception cohort study of pregnancy planners (age, 21-45 years) from the USA and Canada. We estimated fecundability ratios (FR) for maternal age at the participant’s birth using multivariable proportional probabilities regression models. MAIN RESULTS AND THE ROLE OF CHANCE Daughters of mothers ≥30 years were less likely to have previous pregnancies (or pregnancy attempts) or risk factors for infertility, although they were more likely to report that their mother had experienced problems conceiving. The proportion of participants with prior unplanned pregnancies, a birth before age 21, ≥3 cycles of attempt at study entry or no follow-up was greater among daughters of mothers <25 years. Compared with maternal age 25–29 years, FRs (95% CI) for maternal age <20, 20–24, 30–34, and ≥35 were 0.72 (0.61, 0.84), 0.92 (0.85, 1.00), 1.08 (1.00, 1.17), and 1.00 (0.89, 1.12), respectively. LIMITATIONS, REASONS FOR CAUTION Although the examined covariates did not meaningfully affect the associations, we had limited information on the participants’ mother. Differences by maternal age in reproductive history, infertility risk factors and loss to follow-up suggest that selection bias may partly explain our results. WIDER IMPLICATIONS OF THE FINDINGS Our finding that maternal age 35 years or older was not associated with daughter’s fecundability is reassuring, considering the trend towards delayed childbirth. However, having been born to a young mother may be a marker of low fecundability among pregnancy planners. STUDY FUNDING/COMPETING INTEREST(S) PRESTO was funded by NICHD Grants (R21-HD072326 and R01-HD086742) and has received in-kind donations from Swiss Precision Diagnostics, FertilityFriend.com, Kindara.com, and Sandstone Diagnostics. Dr Wise is a fibroid consultant for AbbVie, Inc. TRIAL REGISTRATION NUMBER n/amore » « less
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Climate change is likely to have wide-ranging impacts on maternal and neonatal health in Africa. Populations in low-resource settings already experience adverse impacts from weather extremes, a high burden of disease from environmental exposures, and limited access to high-quality clinical care. Climate change is already increasing local temperatures. Neonates are at high risk of heat stress and dehydration due to their unique metabolism, physiology, growth, and developmental characteristics. Infants in low-income settings may have little protection against extreme heat due to housing design and limited access to affordable space cooling. Climate change may increase risks to neonatal health from weather disasters, decreasing food security, and facilitating infectious disease transmission. Effective interventions to reduce risks from the heat include health education on heat risks for mothers, caregivers, and clinicians; nature-based solutions to reduce urban heat islands; space cooling in health facilities; and equitable improvements in housing quality and food systems. Reductions in greenhouse gas emissions are essential to reduce the long-term impacts of climate change that will further undermine global health strategies to reduce neonatal mortality.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/1471-0528.17622
