Hyperthermia: malformations to chaperones

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.

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.

Heat Stress-Induced Fetal Intrauterine Growth Restriction Is Associated with Elevated LPS Levels Along the Maternal Intestine-Placenta-Fetus Axis in Pregnant Mice

The exacerbation of the greenhouse effect has made heat stress (HS) an important risk factor for the occurrence of intrauterine growth restriction (IUGR). The experiment aims to uncover the effects of maternal HS on IUGR and its mechanisms. The results showed that HS leads to decreased maternal and fetal birth weights, accompanied by increased serum oxidative stress and cortisol levels. Moreover, HS inflicted significant damage to both the intestinal and placental barriers, altering maternal gut microbiota and increasing intestinal LPS levels. As a result, LPS levels increased in maternal serum, placenta, and fetus. Furthermore, HS damaged the intestinal structure, intensifying inflammation and disrupting the redox balance. The placenta exposed to HS exhibited changes in the placental structure along with disrupted angiogenesis and decreased levels of nutritional transporters. Additionally, the leakage of LPS triggered placental JNK and ERK phosphorylation, ultimately inducing severe placental inflammation and oxidative stress. This study suggests that LPS translocation from the maternal intestine to the fetus, due to a disrupted gut microbiota balance and compromised intestinal and placental barrier integrity, may be the primary cause of HS-induced IUGR. Furthermore, increased LPS leakage leads to placental inflammation, redox imbalance, and impaired nutrient transport, further restricting fetal growth.

Ambient temperature and major structural anomalies: A retrospective study of over 2 million newborns

BACKGROUND

Maternal exposure to ambient heat may be associated with congenital anomalies, but evidence is still limited.

OBJECTIVES

We aimed to estimate the association between maternal exposure to ambient heat during the 3-12 weeks post-conception (critical window of organogenesis) and risk of total and various diagnostic categories of major structural anomalies among live singleton births in the contiguous United States (US).

METHODS

We included data on 2,352,529 births with the first day of critical developmental windows falling within months of May through August from 2000 to 2004 across 525 US counties. We used a validated spatial-temporal model to estimate daily county-level population-weighted temperature. We used logistic regression to estimate the association between ambient temperature and risk of diagnostic categories of anomalies during the critical window after adjusting for individual and county-level factors. We conducted subgroup analysis to identify potential susceptible subpopulations.

RESULTS

A total of 29,188 anomalies (12.4 per 1000 births) were recorded during the study period. Maternal exposure to extreme heat (> 95th percentile) was associated with higher risk of total anomalies, central nervous system anomalies, and other uncategorized anomalies with an odds ratio (OR) of 1.05 (95 % CI: 1.00, 1.11), 1.17 (95 % CI: 1.01, 1.37), and 1.16 (95 % CI: 1.04, 1.29) compared with minimum morbidity temperature, respectively. The associations were homogeneous across subgroups defined by maternal age, maternal race/ethnicity, marital status, educational attainment, and parity, but were more pronounced among mothers residing in more socially vulnerable counties and births with multiple anomalies.

CONCLUSIONS

Among US live singleton births, maternal exposure to ambient heat may be associated with higher risk of total anomalies, central nervous system anomalies, and other uncategorized anomalies. We suggest additional research is carried out to better understand the relations between maternal heat exposure and congenital anomalies in the presence of global warming.

The prenatal weekly temperature exposure and neonatal congenital heart disease: a large population-based observational study in China

We aim to explore the link between maternal weekly temperature exposure and CHD in offspring and identify the relative contributions from heat and cold and from moderate and extreme atmospheric temperature. From January 2019 to December 2020, newborns who were diagnosed with CHD by echocardiography in the Network Platform for Congenital Heart Disease (NPCHD) from 11 cities in eastern China were enrolled in the present study. We appraised the exposure lag response relationship between temperature and CHDs in the distributed lag nonlinear model and further probed the pooled estimates by multivariate meta-analysis. We further performed the exposure-response curves in extreme temperature (5th percentile for cold and 95th for hot events). We also delve into the cumulative risk ratios (CRRs) of temperature on CHDs in general and subgroups. In this study, 5904 of 983, 523 infants were diagnosed with CHDs. The temperature-CHD combination performed positive significance in two exposure windows, gestational weeks 10-16 and 26-31, and reached the maximum effect in the 28th week. Compared with extreme cold (5th, 6.14℃), these effects were higher in extreme heat (95th, 29.26℃). The cumulative exposure-response curve showed a steep nonlinear rise in the hot tail but showed non-significance at low temperatures. In this range, the CRRs of temperature showed an increment to a ceiling of 3.781 (95% CI: 1.460-10.723). The temperature- CHD curves for both sex groups showed a general growth trend. No statistical significance was observed between these two groups (P = 0.106). The cumulative effect of the temperature related CHD was significant in regions with lower education levels (maximum CRR was 9.282 (3.019-28.535)). A degree centigrade increase in temperature exposure was associated with the increment of CHD risk in the first and second trimesters, especially in extreme heat. Neonates born in lower education regions were more vulnerable to temperature-related CHDs.

Ambient temperature during pregnancy and fetal growth in Eastern Massachusetts, USA

Background

Left unabated, rising temperatures pose an escalating threat to human health. The potential effects of hot temperatures on fetal health have been under-explored. Here, we examined the association between prenatal ambient temperature exposure and fetal growth measures in a Massachusetts-based pregnancy cohort.

Methods

We used ultrasound measurements of biparietal diameter (BPD), head circumference (HC), femur length and abdominal circumference (AC), in addition to birthweight (BW), from 9446 births at Beth Israel Deaconess Medical Center from 2011 to 2016. Ultrasound scans were classified into three distinct gestational periods: 16–23 weeks, 24–31 weeks, 32+ weeks; and z-scores were created for each fetal growth measure using the INTERGROWTH-21st standards. We fitted distributed lag models to estimate the time-varying association between weekly temperature and fetal growth, adjusting for sociodemographic characteristics, seasonal and long-term trends, humidity and particulate matter (PM2.5).

Results

Higher ambient temperature was associated with smaller fetal growth measures. The critical window of exposure appeared to be Weeks 1–20 for ultrasound parameters, and high temperatures throughout pregnancy were important for BW. Associations were strongest for head parameters (BPD and HC) in early to mid-pregnancy, AC late in pregnancy and BW. For example, a 5ºC higher cumulative temperature exposure was associated with a lower mean AC z-score of -0.26 (95% CI: -0.48, -0.04) among 24–31-Week scans, and a lower mean BW z-score of -0.32 (95% CI: -0.51, -0.12).

Conclusion

Higher temperatures were associated with impaired fetal growth. This has major health implications given that extreme temperatures are more common and escalating.

The association of maternal exposure to ambient temperature with low birth weight in term pregnancies varies by location: In Brazil, positive associations may occur only in the Amazon region

Exposure to ambient temperature has been linked to adverse birth outcomes in several regions, including the USA, Australia, China, countries in the Middle East, and European countries. To date, no studies were performed in South America, a region with serious challenges related to climate change. Our investigation addresses this literature lack by examining the association between Low Birth Weight (LBW) and ambient temperature exposure in the largest county in South America, Brazil. We applied a nationwide case-control study design using a logistic regression model to estimate the odds ratio (OR) for LBW associated with ambient temperature during a specific trimester of pregnancy (1-3 trimester). Our sample size includes 5,790,713 birth records nationwide over 18 years (2001-2018), of which 264,967 infants were included in the model as cases of LBW, representing 4.6% of our total sample. We adjusted our model for several confounding variables, including weather factors, air pollution, seasonality, and SES variables at the individual level. Our findings indicate that North was the only region with positive and statistically significant associations in the primary analysis and most of the sensitivity analysis, which is the region where the Amazon is located. In this region, we estimated an increase of 5.16% (95%CI: 3.60; 6.74) in the odds of LBW per 1 °C increase in apparent temperature when the exposure occurred in the second trimester. Our results may be explained by the climate conditions in the Amazon region in the past years. A large body of literature indicates that the Amazon region has been facing serious climate challenges including issues related to policy, governance, and deforestation. Specifically, regarding deforestation, it is suggested that land use change and deforestation is projected to increase heat stress in the Amazon region, because of Amazon savannization, increasing the risk of heat stress exposure in Northern Brazil. Our study can assist public sectors and clinicians in mitigating the risk and vulnerability of the Amazonian population.

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

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

Modeling complex effects of exposure to particulate matter and extreme heat during pregnancy on congenital heart defects: A U.S. population-based case-control study in the National Birth Defects Prevention Study

BACKGROUND/OBJECTIVE

Research suggests gestational exposure to particulate matter ≤2.5 μm (PM2.5) and extreme heat may independently increase risk of birth defects. We investigated whether duration of gestational extreme heat exposure modifies associations between PM2.5 exposure and specific congenital heart defects (CHDs). We also explored nonlinear exposure-outcome relationships.

METHODS

We identified CHD case children (n = 2824) and non-malformed live-birth control children (n = 4033) from pregnancies ending between 1999 and 2007 in the National Birth Defects Prevention Study, a U.S. population-based multicenter case-control study. We assigned mothers 6-week averages of PM2.5 exposure during the cardiac critical period (postconceptional weeks 3-8) using the closest monitor within 50 km of maternal residence. We assigned a count of extreme heat days (EHDs, days above the 90th percentile of daily maximum temperature for year, season, and weather station) during this period using the closest weather station. Using generalized additive models, we explored logit-nonlinear exposure-outcome relationships, concluding logistic models were reasonable. We estimated joint effects of PM2.5 and EHDs on six CHDs using logistic regression models adjusted for mean dewpoint and maternal age, education, and race/ethnicity. We assessed multiplicative and additive effect modification.

RESULTS

Conditional on the highest observed EHD count (15) and at least one critical period day during spring/summer, each 5 μg/m3 increase in average PM2.5 exposure was significantly associated with perimembranous ventricular septal defects (VSDpm; OR: 1.54 [95% CI: 1.01, 2.41]). High EHD counts (8+) in the same population were positively, but non-significantly, associated with both overall septal defects and VSDpm. Null or inverse associations were observed for lower EHD counts. Multiplicative and additive effect modification estimates were consistently positive in all septal models.

CONCLUSIONS

Results provide limited evidence that duration of extreme heat exposure modifies the PM2.5-septal defects relationship. Future research with enhanced exposure assessment and modeling techniques could clarify these relationships.

Associations between ambient heat exposure early in pregnancy and risk of congenital heart defects: a large population-based study

Some epidemiological studies have confirmed the association between environmental factors and congenital heart defects (CHD). While the possibility that maternal ambient heat exposures are related to CHD has received little attention. Our study aims to investigate the association between maternal ambient extreme heat exposure early in pregnancy and the risk of CHD in offspring in China. We conducted a retrospective cohort study of 1,918,105 fetuses between 2 and 8 weeks after gestation from May to October in Guangdong, China, 2015-2019. The main heat exposure was defined as extreme heat events (EHE) by using the 90th (EHE90) or 95th (EHE95) percentile of the daily maximum temperature. For each EHE definition, we further defined four indicators: having EHE or not, frequency, duration, and cumulative days. We used the log-binomial regression models to calculate the prevalence ratios (PR) of CHD with 95% confidence intervals (CI) for the associations between CHD and EHE, adjusted for potentially confounding covariates. There are 1,918,105 infants included in the study, of which 9588 had CHD, with a prevalence rate of 499.9 per 100,000 (95% CI: 489.9, 509.8). We found that all EHE indicators were positively associated with the increased risks of overall CHD, some CHD classes (congenital malformations of cardiac septa, congenital malformations of great arteries, and congenital malformations of great arteries), and some CHD subtypes (atrial septal defect and patent ductus arteriosus). In addition, the PR yielded higher estimates when exposing to EHE95. For instance, the risk of suffering congenital malformations of great arteries was 1.548 (95% CI: 1.401, 1.712) for EHE90 exposure and 1.723 (95% CI: 1.565, 1.898) for EHE95 exposure, respectively. Our study demonstrated that EHE during 2-8 weeks postconception was associated with overall CHD in offspring, particularly atrial septal defects and patent ductus arteriosus. The associations strengthened with the extent and cumulative days of maternal exposure to EHE.

Low and High Ambient Temperatures during Pregnancy and Birth Weight among 624,940 Singleton Term Births in Israel (2010-2014): An Investigation of Potential Windows of Susceptibility

BACKGROUND

Exposure to heat during pregnancy has been associated with reduced fetal growth. Less is known about associations with cold and the potential for critical time windows of exposure.

OBJECTIVES

We aimed to evaluate, in a national retrospective cohort, critical windows of susceptibility during pregnancy to extreme temperatures (low and high) and fetal growth, among 624,940 singleton term births in Israel during the period 2010-2014.

METHODS

Temperature exposures were estimated using a spatially refined gridded climate data set with a 1-h and 1-km2 resolution. Percentiles of temperature were categorized by climatic zone for the entire pregnancy and by trimesters and weeks. Generalized additive models with the distributed lag nonlinear model framework were used to estimate unadjusted and adjusted associations between percentiles and categories of temperature and fetal growth markers: term [births after 36 weeks of gestational age (GA)] mean birth weight and term low birth weight (tLBW, term infants with birth weight below 2,500g).

RESULTS

After adjustment, extreme temperatures (percentiles) during the entire pregnancy were associated with a lower mean birth weight {≤10th vs. 41st-50th percentile: -56g [95% confidence interval (CI): -63g, -50g)]; >90th vs. 41st-50th percentile: -65g; 95% CI: -72g, -58g}. Similar inverse U-shaped patterns were observed for all trimesters, with stronger associations for heat than for cold and for exposures during the third trimester. For heat, results suggest critical windows between 3-9 and 19-34 GA-weeks, with the strongest association estimated at 3 GA-weeks (temperature >90th vs. 41st-50th percentiles: -3.8g; 95% CI: -7.1g, -0.4g). For cold, there was a consistent trend of null associations early in pregnancy and stronger inverse associations over time, with the strongest association at 36 GA-week (≤10th vs. 41st-50th percentiles: -2.9g; 95% CI: -6.5g, 0.7g). For tLBW, U-shape patterns were estimated for the entire pregnancy and third trimester exposures, as well as nonsignificant associations with heat for 29-36 GA-weeks. Generally, the patterns of associations with temperatures during the entire pregnancy were consistent when stratified by urbanicity and geocoding hierarchy, when estimated for daily minimum and maximum temperatures, when exposures were classified based on temperature distributions in 49 natural regions, and when estimated for all live births.

DISCUSSION

Findings from our study of term live births in Israel (2010-2014) suggest that exposure to extreme temperatures, especially heat, during specific time windows may result in reduced fetal growth. https://doi.org/10.1289/EHP8117.

Nonmedical Determinants of Congenital Heart Diseases in Children from the Perspective of Mothers: A Qualitative Study in Iran

Introduction

Mortality due to noncommunicable diseases has increased in the world today with the advent of demographic shifts, growing age, and lifestyle patterns in the world, which have been affected by economic and social crises. Congenital heart defects are one of the forms of diseases that have raised infant mortality worldwide. The objective of present study was to identify nonmedical determinants related to this abnormality from the mother's perspectives.

Methods

This research was a qualitative study and the data collection method was a semistructured interview with mothers who had children with congenital heart diseases referring to the Shahid Rajaei Heart Hospital in Tehran, Iran. A thematic analysis approach was employed to analyze transcribed documents assisted by MAXQDA Plus version 12.

Results

Four general themes and ten subthemes including social contexts (social harms, social interactions, and social necessities), psychological contexts (mood disorders and mental well-being), cultural contexts (unhealthy lifestyle, family culture, and poor parental health behaviors), and environmental contexts (living area and polluted air) were extracted from interviews with mothers of children with congenital heart diseases.

Conclusions

Results suggest that factors such as childhood poverty, lack of parental awareness of congenital diseases, lack of proper nutrition and health facilities, education, and lack of medical supervision during pregnancy were most related with the birth of children with congenital heart disease from mothers' prospective. In this regard, targeted and intersectorial collaborations are proposed to address nonmedical determinants related to the incidence of congenital heart diseases.

Independent and interactive effects of air pollutants and ambient heat exposure on congenital heart defects

Accumulating studies have been focused on the independent effects of air pollutants and ambient heat exposure on congenital heart defects (CHDs) but with inconsistent results, and their interactive effect remains unclear. A case-control study including 921 cases and 9210 controls was conducted in Changsha, China in warm season in 2015-2018. The gravidas were assigned monthly averages of daily air pollutants and daily maximum temperature using the nearest monitoring station method and city-wide average method, respectively, during the first trimester of pregnancy. Multivariate logistic regression models were used to estimate the independent effects of each air pollutant and different ambient heat exposure indicators. Their additive joint effects were quantified using attribute proportions of interaction (API). Increasing SO₂ consistently increased the risk of CHDs in the first trimester of pregnancy, with aORs ranging from 1.78 to 2.04. CO, NO₂ and PM_2.5 exposure in the first month of pregnancy, and O₃ exposure in the second and third month of pregnancy were also associated with elevated risks of CHDs, with aORs ranging from 1.04 to 1.15. Depending on the ambient heat exposure indicator used, air pollutants showed more apparent synergistic effects (API > 0) with less and moderately intense heat exposure. Maternal exposure to CO, NO₂, SO₂, PM_2.5 and O₃ during early pregnancy increased risk of CHDs, and ambient heat exposure may enhance these effects. Our findings help to understand the interactive effect of air pollution with ambient heat exposure on CHDs, which is of vital public health significance.

Ambient extreme heat exposure in summer and transitional months and emergency department visits and hospital admissions due to pregnancy complications

Although extreme heat exposure (EHE) was reported to be associated with increased risks of multiple diseases, little is known about the effects of EHE on pregnancy complications. We examined the EHE-pregnancy complications associations by lag days, subtypes, sociodemographic characteristics, and areas in New York State (NYS). We conducted a case-crossover analysis to assess the EHE-pregnancy complications associations in summer (June-August) and transitional months (May and September). All emergency department (ED) visits and hospital admissions due to pregnancy complications (ICD 9 codes: 630-649) from 2005 to 2013 in NYS were included. Daily mean temperature > 90th percentile of the monthly mean temperature in each county was defined as an EHE. We used conditional logistic regression while controlling for other weather factors, air pollutants and holidays to assess the EHE-pregnancy complications associations. EHE was significantly associated with increased ED visits for pregnancy complications in summer (ORs ranged: 1.01-1.04 from lag days 0-5). There was also a significant and stronger association in transitional months (ORs ranged: 1.02-1.06, Lag 0). Furthermore, we found EHE affected multiple subtypes of pregnancy complications, including threatened/spontaneous abortion, renal diseases, infectious diseases, diabetes, and hypertension (ORs range: 1.13-1.90) during transitional months. A significant concentration response effect between the number of consecutive days of EHE and ED visits in summer (P for trend <0.001), ED visits in September (P for trend =0.03), and hospital admission in May (P for trend<0.001) due to pregnancy complications was observed, respectively. African Americans and residents in lower socioeconomic position (SEP) counties were more susceptible to the effects of EHE. In conclusion, we found an immediate and prolonged effect of EHE on pregnancy complications in summer and a stronger, immediate effect in transitional months. These effects were stronger in African Americans and counties with lower SEP. Earlier warnings regarding extreme heat are recommended to decrease pregnancy complications.

Impact of ambient temperature on ovarian reserve

OBJECTIVE

To examine the association between ambient temperature and antral follicle count (AFC), a standard measure of ovarian reserve.

DESIGN

Prospective cohort study.

SETTING

Fertility center at an academic hospital in the northeastern United States.

PATIENT(S)

631 women attending the Massachusetts General Hospital Fertility Center (2005-2015) who participated in the Environment and Reproductive Health Study.

INTERVENTION(S)

Daily temperature at the women's residential address was estimated for the 90 days before their antral follicle scan using a spatially refined gridded climate data set. We evaluated the associations between temperature and AFC using Poisson regression with robust standard errors, adjusting for relative humidity, fine particulate matter exposure, age, education, smoking status, year and month of AFC, and diagnosis of diminished ovarian reserve and ovulation disorders.

MAIN OUTCOME MEASURE(S)

Antral follicle count as measured with transvaginal ultrasonography.

RESULT(S)

A 1°C increase in average maximum temperature during the 90 days before ovarian reserve testing was associated with a -1.6% (95% confidence interval [CI], -2.8, -0.4) lower AFC. Associations remained negative, but were attenuated, for average maximum temperature exposure in the 30 days (-0.9%, 95% CI, -1.8, 0.1) and 14 days (-0.8%, 95% CI, -1.6, 0.0) before AFC. The negative association between average maximum temperature and AFC was stronger in November through June than during the summer months, suggesting that timing of heat exposure and acclimatization to heat may be important factors to consider in future research.

CONCLUSION(S)

Exposure to higher temperatures was associated with lower ovarian reserve. These results raise concern that rising ambient temperatures worldwide may result in accelerated reproductive aging among women.

A Comprehensive Assessment of the Associations Between Season of Conception and Birth Defects, Texas, 1999-2015

Birth defects prevalence may vary seasonally, but previous studies have focused on a few commonly occurring phenotypes. We performed a phenome-wide association study (PheWAS) in order to evaluate the associations between season of conception and a broad range of birth defects. Date of conception was estimated for all livebirths and birth defect cases in Texas from 1999-2015 using data from vital records, provided by the Texas Department of State Health Services Center for Health Statistics. Birth defects diagnoses were obtained from the Texas Birth Defects Registry, a statewide, active surveillance system. We estimated prevalence ratios (PRs) for phenotypes with ≥50 cases according to conception in spring (March-May), summer (June-August) or fall (September-November) relative to winter (December-February), using Poisson regression. Season of conception was associated with 5% of birth defects studied in models adjusted for maternal age, education, race/ethnicity, and number of previous livebirths. Specifically, summer conception was associated with any monitored birth defect (PR 1.03, 95% CI 1.02-1.04) and five specific phenotypes, most notably Hirschsprung disease (PR 1.46, 95% CI 1.22-1.75). These findings suggest that seasonally variable exposures influence the development of several birth defects and may assist in identifying novel environmental risk factors.

Projected Changes in Maternal Heat Exposure During Early Pregnancy and the Associated Congenital Heart Defect Burden in the United States

Background More intense and longer-lasting heat events are expected in the United States as a consequence of climate change. This study aimed to project the potential changes in maternal heat exposure during early pregnancy (3-8 weeks post conception) and the associated burden of congenital heart defects ( CHD s) in the future. Methods and Results This study expanded on a prior nationwide case-control study that evaluated the association between CHD s and maternal heat exposure during early pregnancy in summer and spring. We defined multiple indicators of heat exposure, and applied published odds ratios obtained for the matching season of the baseline (1995-2005) into the projection period (2025-2035) to estimate potential changes in CHD burden throughout the United States. Increases in maternal heat exposure were projected across the United States and to be larger in the summer. The Midwest will potentially have the highest increase in summer maternal exposure to excessively hot days (3.42; 95% CI, 2.99-3.88 per pregnancy), heat event frequency (0.52; 95% CI, 0.44-0.60) and heat event duration (1.73; 95% CI, 1.49-1.97). We also found large increases in specific CHD subtypes during spring, including a 34.0% (95% CI, 4.9%-70.8%) increase in conotruncal CHD in the South and a 38.6% (95% CI , 9.9%-75.1%) increase in atrial septal defect in the Northeast. Conclusions Projected increases in maternal heat exposure could result in an increased CHD burden in certain seasons and regions of the United States.

Maternal ambient heat exposure during early pregnancy in summer and spring and congenital heart defects - A large US population-based, case-control study

BACKGROUND/OBJECTIVE

Few studies have assessed the effect of ambient heat during the fetal development period on congenital heart defects (CHDs), especially in transitional seasons. We examined and compared the associations between extreme heat and CHD phenotypes in summer and spring, assessed their geographical differences, and compared different heat indicators.

METHODS

We identified 5848 CHD cases and 5742 controls (without major structural defects) from the National Birth Defects Prevention Study, a US multicenter, population-based case-control study. Extreme heat events (EHEs) were defined by using the 95th (EHE95) or 90th (EHE90) percentile of daily maximum temperature and its frequency and duration during postconceptional weeks 3-8. We used a two-stage Bayesian hierarchical model to examine both regional and study-wide associations. Exposure odds ratios (ORs) were calculated using multivariate logistic regression analyses, while controlling for potential confounding factors.

RESULTS

Overall, we observed no significant relationships between maternal EHE exposure and CHDs in most regions during summer. However, we found that 3-11 days of EHE90 during summer and spring was significantly associated with ventricular septal defects (VSDs) study-wide (ORs ranged: 2.17-3.24). EHE95 in spring was significantly associated with conotruncal defects and VSDs in the South (ORs: 1.23-1.78). Most EHE indicators in spring were significantly associated with increased septal defects (both VSDs and atrial septal defects (ASDs)) in the Northeast.

CONCLUSION

While generally null results were found, long duration of unseasonable heat was associated with the increased risks for VSDs and ASDs, mainly in South and Northeast of the US. Further research to confirm our findings is needed.

Influence of hyperthermal regimes on experimental teratoma development in vitro

We screened for the impact of hyperthermal regimes varying in the cumulative equivalent minutes at 43°C (CEM43°C) and media composition on tumour development using an original teratoma in vitro model. Rat embryos (three germ layers) were microsurgically isolated and cultivated at the air‐liquid interface. During a two week period, ectodermal, mesodermal and endodermal derivatives developed within trilaminar teratomas. Controls were grown at 37°C. Overall growth was measured, and teratoma survival and differentiation were histologically assessed. Cell proliferation was stereologically quantified by the volume density of Proliferating Cell Nuclear Antigen. Hyperthermia of 42°C, applied for 15 minutes after plating (CEM43°C 3.75 minutes), diminished cell proliferation (P ˂ .0001) and enhanced differentiation of both myotubes (P ˂ .01) and cylindrical epithelium (P ˂ .05). Hyperthermia of 43°C applied each day for 30 minutes during the first week (CEM43°C 210 minutes) impaired overall growth (P ˂ .01) and diminished cell proliferation (P ˂ .0001). Long‐term hyperthermia of 40.5°C applied for two weeks (CEM43°C 630 minutes) significantly impaired survival (P ˂ .005). Long‐term hyperthermia of 40.5°C applied from the second day when differentiation of tissues begins (CEM43°C 585 minutes) impaired survival (P ˂ .0001), overall growth (P ˂ .01) and cartilage differentiation (P ˂ .05). No teratomas survived extreme regimes: 43°C for 24 hours (CEM43°C 1440 minutes), hyperthermia in the scant serum‐free medium (CEM43°C 630 minutes) or treatment with an anti‐HSP70 antibody before long‐term hyperthermia 40.5°C from the second day (CEM43°C 585 minutes). This in vitro research provided novel insights into the impact of hyperthermia on the development of experimental teratomas from their undifferentiated sources and are thus of potential interest for future therapeutic strategies in corresponding in vivo models.

Congenital heart defects of fetus after maternal exposure to organic and inorganic environmental factors: a cohort study

Objective

Maternal exposure to various contaminants has been reported to be correlated with congetinal heart defects (CHDs). In this study, the effect of maternal exposure to organic and inorganic environmental factors upon the incidence of CHDs was investigated. We conducted a retrospective birth cohort study of infants born in the Maternal and Child Health Hospital of Panyu District in Guangzhou.

Materials and Methods

A total of 5381 cases with complete medical records, including mothers, fathers, and infants, were enrolled. The relationship between maternal occupational exposure to hazardous substances and strong noise during pregnancy and CHDs was analyzed. Occupational exposure to hazardous substances increased the incidence of CHDs.

Results

Forty-eight of 145 mothers (33.1%) in the CHDs group worked in hazardous and strong noise factories, while the corresponding percentage mothers in the control group was 22.8% (1193/5236). The percentage of mothers with a history of contact with organic solvents and exposure to strong noise in the CHDs group was significantly higher than the control group. There was no significant difference in the histories of contact with heavy metals, high temperatures, and other extreme environments between two groups.

Conclusions

Hazardous substances in factories, especially organic solvents, were identified as potential risk factors for CHDs. Besides, exposure to high noise also increased the incidence of CHDs.

Risk of Congenital Heart Defects after Ambient Heat Exposure Early in Pregnancy

BACKGROUND

Congenital heart defects may be environmentally related, but the association with elevated ambient temperature has received little attention.

OBJECTIVES

We studied the relationship between outdoor heat during the first trimester of pregnancy and risk of congenital heart defects.

METHODS

We carried out a retrospective cohort study of 704,209 fetuses between 2 and 8 weeks postconception from April to September in Quebec, Canada, 1988-2012. We calculated the prevalence of congenital heart defects at birth according to the number of days women were exposed to maximum temperature ≥ 30°C. In log-binomial regression models, we estimated prevalence ratios (PR) and 95% confidence intervals (CI) for the relationship of temperature with seven critical and eight noncritical heart defects, adjusted for pregnancy characteristics.

RESULTS

Prevalence of congenital heart defects was 979.5 per 100,000 for 10 days or more of temperature ≥ 30°C compared with 878.9 per 100,000 for 0 days of exposure. Temperature was more precisely associated with noncritical than critical defects, which had lower prevalence. Fetuses exposed to 15 days of temperature ≥ 30°C between 2 and 8 weeks postconception had 1.06 times the risk of critical defects (95% CI: 0.67, 1.67) and 1.12 times the risk of noncritical defects (95% CI: 0.98, 1.29) relative to 0 days. Associations were higher for atrial septal defects (PR 1.37, 95% CI: 1.10, 1.70) than for other noncritical defects. For atrial septal defects, associations with elevated temperatures began the 3rd week postconception.

CONCLUSIONS

Extreme heat exposure during the first trimester may be associated with noncritical heart defects, especially of the atrial septum. Citation: Auger N, Fraser WD, Sauve R, Bilodeau-Bertrand M, Kosatsky T. 2017. Risk of congenital heart defects after ambient heat exposure early in pregnancy. Environ Health Perspect 125:8-14; http://dx.doi.org/10.1289/EHP171.

Does maternal exposure during pregnancy to higher ambient temperature increase the risk of hypospadias?

INTRODUCTION

The association between ambient temperature that the mother is exposed to during pregnancy and hypospadias has not been investigated by the studies, although the recent studies showed the correlation between some congenital malformations (congenital heart disease, neural tube defect, etc.) and ambient temperature.

OBJECTIVE

The aim was to investigate the relation between hypospadias and the ambient temperatures that the mother is exposed to during her pregnancy.

METHODS

The data of patients with hypospadias that had their gestational periods in Ankara and Istanbul regions, and had other urological treatments (circumcision, urinary tract infection, pyeloplasty, nephrolithotomy, etc.) between January 2000 and November 2015 were analyzed retrospectively. The ambient temperature at 8-14 weeks of gestation was investigated for each patient by reviewing the data of the General Directorate of Meteorology, since this period was risky for development of hypospadias. The data including ambient temperature that the pregnant mother was exposed to, maternal age, parity, economical status, gestational age at birth, and birth weight were compared between two groups. The retrospective nature of the study may be a potential source for selection bias.

RESULTS

The data of 1,709 children that had hypospadias repair and 4,946 children that had other urological treatments between 2000 and 2015 were retrospectively analyzed. There were no differences between the groups for maternal age, parity, economical status, gestational age at birth, and birth weight (Table). Analysis of exposed maximum and average ambient temperatures at 8-14 weeks of gestation revealed that July and August, hot periods in summer time, were more prevalent in the hypospadias group (p = 0.01). The average and maximum monthly ambient temperatures during summer increased the risk for hypospadias (OR, 1.32; 95% CI, 1.08-1.52; and OR, 1.22; 95% CI, 0.99-1.54, respectively.

CONCLUSIONS

In this paper, we evaluated the relation between hypospadias and the ambient temperatures that the mother is exposed during her pregnancy. The results of this study indicated that the high ambient temperatures the mother and fetus are exposed to at 8-14 weeks of gestation increased the risk of hypospadias in the offspring.

Ambient temperature and congenital heart defects

STUDY QUESTION

Does maternal exposure during pregnancy to higher ambient temperature increase the risk of congenital heart defects (CHDs)?

SUMMARY ANSWER

Significant associations were found between maternal exposure during pregnancy to higher ambient temperature and CHDs risk especially during the cold season.

WHAT IS KNOWN ALREADY

From rodents to non-human primates, a teratogenic effect of hyperthermic insult has been demonstrated. There are fewer data regarding the effect on the human fetus and specifically the association between maternal exposures during pregnancy to higher ambient temperature and CHDs.

STUDY DESIGN, SIZE, DURATION

This population registry-based cohort study included 135 527 live and stillbirths in the Tel-Aviv region of Israel in 2000-2006.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two clinical diagnostic groups of isolated cardiac defects (atrial septal defects and ventricular septal defects: n = 542 and 481, respectively) and one group of multiple cardiac defects (defined by the presence of two or more cardiac malformations, n = 607) were studied. Temperature measurements were constructed from ambient stations and used to assess the impact of maternal exposure to average ambient temperature and extreme heat events (daily average temperature above the 90th percentile) during Weeks 3-8 of pregnancy on risk of CHDs. Logistic models, adjusted for sociodemographic covariates, were used to evaluate the associations between temperature and CHDs.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, we found no significant associations between ambient temperature and CHDs throughout the year, with one exception for multiple CHDs. After stratifying by season of conception, continuous exposure to average ambient temperature and maximum peak temperature (1°C increase) during the cold season increased the risk for multiple CHDs [odds ratio (OR) 1.05, 95% confidence interval (CI): 1.00, 1.10 and OR 1.03, 95% CI: 1.01, 1.05, respectively]. A 1-day increase in extreme heat events increased the risk for multiple CHDs (OR 1.13, 95% CI: 1.06, 1.21) and also for isolated atrial septal defects (OR 1.10, 95% CI: 1.02, 1.19).

LIMITATIONS, REASONS FOR CAUTION

Information both on CHD cases and on ambient temperature was based on registries and it is possible that this may cause some misclassification. In urban areas, pregnant women may be exposed to higher temperatures than recorded by ambient monitors because of the 'heat island effect'. Furthermore, data for the amount of time spent indoors were unavailable and this could have resulted in exposure misclassification.

WIDER IMPLICATIONS OF THE FINDINGS

The findings are important within the context of global climate change, which may have implications for public health in countries with mild winters and hot summers.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Israeli Ministry of Environmental Protection (research grant-7-2-7) and by the Environment and Health Fund (PhD Fellowship Program). There are no competing interests.

Clinical, genetic and environmental factors associated with congenital vertebral malformations

Congenital vertebral malformations (CVM) pose a significant health problem because they can be associated with spinal deformities, such as congenital scoliosis and kyphosis, in addition to various syndromes and other congenital malformations. Additional information remains to be learned regarding the natural history of congenital scoliosis and related health problems. Although significant progress has been made in understanding the process of somite formation, which gives rise to vertebral bodies, there is a wide gap in our understanding of how genetic factors contribute to CVM development. Maternal diabetes during pregnancy most commonly contributes to the occurrence of CVM, followed by other factors such as hypoxia and anticonvulsant medications. This review highlights several emerging clinical issues related to CVM, including pulmonary and orthopedic outcome in congenital scoliosis. Recent breakthroughs in genetics related to gene and environment interactions associated with CVM development are discussed. The Klippel-Feil syndrome which is associated with cervical segmentation abnormalities is illustrated as an example in which animal models, such as the zebrafish, can be utilized to provide functional evidence of pathogenicity of identified mutations.

Genetic aspects of congenital and idiopathic scoliosis

Congenital and idiopathic scoliosis represent disabling conditions of the spine. While congenital scoliosis (CS) is caused by morphogenic abnormalities in vertebral development, the cause(s) for idiopathic scoliosis is (are) likely to be varied, representing alterations in skeletal growth, neuromuscular imbalances, disturbances involving communication between the brain and spine, and others. Both conditions are characterized by phenotypic and genetic heterogeneities, which contribute to the difficulties in understanding their genetic basis that investigators face. Despite the differences between these two conditions there is observational and experimental evidence supporting common genetic mechanisms. This paper focuses on the clinical features of both CS and IS and highlights genetic and environmental factors which contribute to their occurrence. It is anticipated that emerging genetic technologies and improvements in phenotypic stratification of both conditions will facilitate improved understanding of the genetic basis for these conditions and enable targeted prevention and treatment strategies.