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Map of Sweden showing the distribution of temperatures ( • C) by the 50th and 95th percentiles by municipalities.
Source publication
Background
Evidence indicates that high temperatures are a risk factor for preterm birth. Increasing heat exposures due to climate change are therefore a concern for pregnant women. However, the large heterogeneity of study designs and statistical methods across previous studies complicate interpretation and comparisons. We investigated association...
Contexts in source publication
Context 1
... initial hypothesis was that the pregnant women would be at higher risk to large changes of ambient temperature relative to their own geographical area, as humans tend to be more adaptive to their local climate ( Basagaña et al., 2021;Hondula et al., 2015). In addition, in Sweden the temperatures vary substantially between North and South regions (Fig. 2). For this, we estimated the percentiles of daily temperatures among women living in the same municipality across Sweden (N • of municipalities = 290) and used them as individual exposures rather than absolute temperature values. Then, we used the daily percentile data to estimate average weekly percentiles from date of birth until 39 ...
Context 2
... the curves, risks were extrapolated comparing temperatures above the 90th, 95th or 99th percentiles versus the 50th percentile of municipality-specific exposure distribution. For quantile regression and time-to-event analysis only, we selected the covariates using directed acyclic graph (DAG; Supplement Fig. S2). This included month and year of conception, region, BMI, maternal education, and maternal age. ...
Context 3
... Fig. 2 we present the ambient temperature values corresponding to the 50th and 95th percentiles of municipality-specific distributions across Sweden. The ambient temperature varied between 1 • C and 10 • C in the 50th percentile whereas in the 95th percentile it varied between 13 • C and 20 • C. In addition, in the highest percentile, we ...
Context 4
... observed consistent results in the three different analytical approaches: the case-crossover design, quantile regression and time-toevent analyses. Most studies found positive associations between elevated temperature and preterm births using mainly time-series designs ( Liang et al., 2016;Schifano et al., 2013a;Vicedo-Cabrera et al., 2014), case-crossover designs (Auger et al., 2015; Basu et al., 2010) and Table 1 Descriptive of the population by subcategories of preterm births. Values are mean (SD) for continuous normal distributed variables, median (interquartile range) for continuous non-normal distributed variables, and percentage for categorical variables. ...
Context 5
... variability in exposure, and lack rural coverage, thus limiting the generalizability of the results to the general population (Kloog, 2019). In our spatiotemporal models, we were able to assign daily exposure at the residential address of each individual, and to convert absolute temperature values in municipality-specific percentiles (Fig. 2). Another strength is the large sample size (over 560,000 pregnant women) with a high representativeness as the SPR covered more than 90% of all deliveries in the entire country of Sweden between 2014 and 2019. Besides a high-quality assessment of the study outcome (preterm birth), the SPR also provides a large amount of relevant ...
Citations
... Since it is important to identify the determinants of PTB for prevention and control, previous studies have tried to establish a causal association between potential risk factors and PTB. Although previous studies have investigated the associations between PTB and high ambient temperature, discrepancies remain across these studies [4,[10][11][12]. These varying results could be related to numerous contributing factors (at the individual or regional level), which modify the effect of ambient temperature on PTB, including maternal age, maternal socioeconomic status, regional urbanicity, and greenness. ...
Background
Several studies have reported that climate change elevates heat exposure in pregnant women and high temperatures during pregnancy are associated with preterm births (PTBs). Although the association might be disproportionate, related evidence remains sparse. We evaluated the disproportionate risk of PTB associated with ambient temperature during pregnancy by individual and regional characteristics in South Korea.
Methods
We collected data on birth certificates and daily mean temperatures during the period from 2011 to 2019. A time-stratified case-crossover design was used to investigate the association between temperature and PTB and stratified analyses were conducted to examine the effect modification of individual and regional characteristics.
Results
A total of 160,067 singleton PTBs were recorded in Korea from 2011 to 2019. A 5℃ increase in the mean temperature during the last four weeks before delivery was associated with an increased risk of PTB with an odds ratio (OR) of 1.03 (95% confidence interval [CI]: 1.02, 1.05), and the association was more evident in mothers aged ≥35 years (OR: 1.06 [95% CI: 1.03, 1.10]) and with low education levels (OR: 1.04 [95% CI: 1.02, 1.05]). Additionally, the estimated risk was evident in districts with lower medical resources and more prominent disparities were shown by individual and regional characteristics in rural areas than in urban areas.
Conclusions
This study provides evidence that the risk of PTB related to ambient temperature is disproportionate by individual and regional characteristics and suggests the need for public health policies to alleviate the disparities, especially in rural areas.
... Time-to-event analyses increases statistical power as all participants at risk are included, there is control of temporal trends (eg, gestational age), and it can be used to investigate windows of susceptibility. 64 Longitudinal random forests are a machine learning approach that can be used to identify longitudinal exposure-related predictors of health. 65 In addition, the attributable risk of heat to adverse outcomes will be calculated as per the described methodologies by the Intergovernmental Panel on Climate Change. ...
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.
... Since it is important to identify the determinants of PTB for prevention and control, previous studies have tried to establish a causal association between potential risk factors and PTB. Although previous studies have investigated the associations between PTB and high ambient temperature, discrepancies remain across these studies [4,[10][11][12]. These varying results could be related to numerous contributing factors (at the individual or regional level), which modify the effect of ambient temperature on PTB, including maternal age, maternal socioeconomic status, regional urbanicity, and greenness. ...
Background
Several studies have reported that high temperatures during pregnancy are associated with preterm births (PTBs). Although the association might be disproportionate, related evidence remains sparse. We evaluated the disproportionate risk of PTB associated with ambient temperature during pregnancy by individual and regional characteristics in South Korea.
Methods
We collected data on birth certificates and daily mean temperatures during the period from 2011 to 2019. A time-stratified case-crossover design was used to investigate the association between temperature and PTB and stratified analyses were conducted to examine the effect modification of individual and regional characteristics.
Results
A total of 160,067 singleton PTBs were recorded in Korea from 2011 to 2019. A 5℃ increase in the mean temperature during the last four weeks before delivery was associated with an increased risk of PTB with an odds ratio (OR) of 1.03 (95% confidence interval [CI]: 1.02, 1.05), and the association was more evident in mothers aged ≥ 35 years (OR: 1.06 [95% CI: 1.03, 1.10]) and with low education levels (OR: 1.04 [95% CI: 1.02, 1.05]). Additionally, the estimated risk was evident in districts with lower medical resources and more prominent disparities were shown by individual and regional characteristics in rural areas than in urban areas.
Conclusions
This study provides evidence that the risk of PTB related to ambient temperature is disproportionate by individual and regional characteristics and suggests the need for public health policies to alleviate the disparities, especially in rural areas.
... To the best of our knowledge, there are no published interventions that have been codesigned to reduce the impact of ambient heat exposure on pregnant, postpartum and neonatal health, and particularly in hot arid and semi-arid areas such as Kilifi, Kenya. There is a growing body of evidence on the impacts of heat on these populations but limited research on the interventions to reduce such risks (16)(17)(18)(19)(20)(21)(22). It is therefore imperative to codesign contextualized interventions for mitigating effects of extreme heat exposure. ...
Background
Ambient heat exposure is increasing due to climate change and is known to affect the health of pregnant and postpartum women, and their newborns. Evidence for the effectiveness of interventions to prevent heat health outcomes in east Africa is limited. Codesigning and integrating local-indigenous and conventional knowledge is essential to develop effective adaptation to climate change.
Methods
Following qualitative research on heat impacts in a community in Kilifi, Kenya, we conducted a two-day codesign workshop to inform a set of interventions to reduce the impact of heat exposure on maternal and neonatal health. Participants were drawn from a diverse group of purposively selected influencers, implementers, policy makers, service providers and community members. The key domains of focus for the discussion were: behavioral practices, health facilities and health system factors, home environment, water scarcity, and education and awareness. Following the discussions and group reflections, data was transcribed, coded and emerging intervention priorities ranked based on the likelihood of success, cost effectiveness, implementation feasibility, and sustainability.
Results
Twenty one participants participated in the codesign discussions. Accessibility to water supplies, social behavior-change campaigns, and education were ranked as the top three most sustainable and effective interventions with the highest likelihood of success. Prior planning and contextualizing local set-up, cross-cultural and religious practices and budget considerations are important in increasing the chances of a successful outcome in codesign.
Conclusion
Codesign of interventions on heat exposure with diverse groups of participants is feasible to identify and prioritize adaptation interventions. The codesign workshop was used as an opportunity to build capacity among facilitators and participants as well as to explore interventions to address the impact of heat exposure on pregnant and postpartum women, and newborns. We successfully used the codesign model in co-creating contextualized socio-culturally acceptable interventions to reduce the risk of heat on maternal and neonatal health in the context of climate change. Our interventions can be replicated in other similar areas of Africa and serve as a model for co-designing heat-health adaptation.
... [9][10][11][12][13] Clearly, the women assessed in these studies were mostly fully acclimatized to high ambient temperatures, [14][15][16][17][18][19] whereas studies from geographical regions with temperate climate remain sparse. [20][21][22][23] Pregnancy complications that these studies focused on include low fetal weight, stillbirth and preterm birth, the latter defined as delivery of the baby before 37 completed weeks of gestation. 11,24,25 Preterm birth affects approximately 11% of all pregnancies worldwide and is one of the most common causes for infant morbidity and mortality. ...
Background:
Climate change, in particular the exposure to heat, impacts on human health and can trigger diseases. Pregnant people are considered a vulnerable group given the physiological changes during pregnancy and the potentially long-lasting consequences for the offspring. Evidence published to date on higher risk of pregnancy complications upon heat stress exposure are from geographical areas with high ambient temperatures. Studies from geographic regions with temperate climates are sparse; however, these areas are critical since individuals may be less equipped to adapt to heat stress. This study addresses a significant gap in knowledge due to the temperature increase documented globally.
Methods:
Birth data of singleton pregnancies (n = 42,905) from a tertiary care centre in Hamburg, Germany, between 1999 and 2021 were retrospectively obtained and matched with climate data from the warmer season (March to September) provided by the adjacent federal meteorological station of the German National Meteorological Service to calculate the relative risk of heat-associated preterm birth. Heat events were defined by ascending temperature percentiles in combination with humidity over exposure periods of up to 5 days. Further, ultrasound data documented in a longitudinal prospective pregnancy cohort study (n = 612) since 2012 were used to identify pathophysiological causes of heat-induced preterm birth.
Findings:
Both extreme heat and prolonged periods of heat exposure increased the relative risk of preterm birth (RR: 1.59; 95% CI: 1.01-2.43; p = 0.045; RR: 1.20; 95% CI: 1.02-1.40; p = 0.025). We identified a critical period of heat exposure during gestational ages 34-37 weeks that resulted in increased risk of late preterm birth (RR: 1.67; 95% CI: 1.14-1.43; p = 0.009). Pregnancies with a female fetus were more prone to heat stress-associated preterm birth. We found heat exposure was associated with altered vascular resistance within the uterine artery.
Interpretation:
Heat stress caused by high ambient temperatures increases the risk of preterm birth in a geographical region with temperate climate. Prenatal routine care should be revised in such regions to provide active surveillance for women at risk.
Funding:
Found in acknowledgements.
Extreme heat events affect both pregnant women and their infants. We applied a time-stratified case-crossover design including 124,819 singleton births in a prospective observational study in 16 hospitals in Benin, Malawi, Tanzania, and Uganda to investigate the association between extreme heat and timing of perinatal death.
We observed weak associations between heat exposure and perinatal mortality with an odds ratio of 1.22 (95%CI 0.85-1.73) for stillbirths; 1.10 (95%CI 0.51-2.34) for antepartum and 1.54 (95%CI 0.63-3.73) for intrapartum stillbirths; and 1.17 (95%CI 0.84-2.61) for perinatal deaths with an increase from 75th to 99th percentile in mean temperature one week (lag 0-6 days) before childbirth. The cumulative exposure-response curve suggested the steepest slope for heat was in intrapartum stillbirths, and stronger associations during the hottest seasons. We conclude that higher temperatures may have short-term effects on mortality risks, particularly for intrapartum stillbirths, raising the importance of improved intrapartum care.
Abstract
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.
Introduction:
High workplace/ambient temperatures have been associated with Adverse Pregnancy Outcomes (APO). Millions of women working in developing nations suffer due to the rising temperatures caused by climate change. There are few pieces of research linking occupational heat stress to APO, and fresh evidence is required.
Methodology:
We used databases including PubMed, Google Scholar, and Science Direct to search for research on high ambient/workplace temperatures and their effects. Original articles, newsletters, and book chapters were examined. The literature we analysed was categorised as follows: Heat, strain, and physical activity harming both mother and fetus. After categorising the literature, it was examined to identify the major results.
Results:
We found a definite association between heat stress and APOs such as miscarriages, premature birth, stillbirth, low birthweight, and congenital abnormalities in 23 research articles. Our work provides important information for future research into the biological mechanisms that create APOs and various prevention measures.
Conclusion:
Our data suggest that temperature has long-term and short-term effects on maternal and fetal health. Though small in number, this study stressed the need for bigger cohort studies in tropical developing countries to create evidence for coordinated policies to safeguard pregnant women.
