Marianne Bilodeau-Bertrand

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

Elevated outdoor temperatures and risk of stillbirth

Background The causes of stillbirth are poorly understood, including whether elevated outdoor temperatures increase risk. We assessed the relationship between elevated ambient temperatures and risk of stillbirth by gestational age and cause of death during warm months in a temperate region. Methods We performed a case-crossover study of 5047 stillbirths in continental Quebec, Canada, between the months of April through September from 1981 to 2011. Using data on maximum daily temperatures adjusted for relative humidity, we estimated associations with stillbirth, comparing temperatures before fetal death with temperatures on adjacent days. The main outcomes were stillbirth according to age of gestation (term, preterm), and cause of death (undetermined, maternal, placenta/cord/membranes, birth asphyxia, congenital anomaly, other). Results Elevated outdoor temperatures the week before the death were more strongly associated with risk of term than preterm stillbirth. Odds of term stillbirth for temperature 28 °C the day before death were 1.16 times greater relative to 20 °C (95% confidence interval, CI 1.02-1.33). Elevated outdoor temperature was associated with stillbirth due to undetermined and maternal causes, but not other causes. Compared with 20 °C, the odds of stillbirth at 28 °C were 1.19 times greater for undetermined causes (95% CI 1.02-1.40) and 1.46 times greater for maternal complications (95% CI 1.03-2.07). Conclusions Elevated outdoor temperatures may be a risk factor for term stillbirth, including stillbirth due to undetermined causes or maternal complications.

Association between quantity and duration of snowfall and risk of myocardial infarction

BACKGROUND: Although aggregate data suggest a link between snowfall and myocardial infarction (MI), individual risk has yet to be assessed. We evaluated the association between quantity and duration of snowfall and the risk of MI using nonaggregated administrative health data. METHODS: We used a case–crossover study design to investigate the association between snowfall and hospital admission or death due to MI in the province of Quebec, Canada, between November and April during 1981–2014. The main exposure measures were quantity (in centimetres) and duration (in hours) of snowfall by calendar day. We computed odds ratios (ORs) and 95% confidence intervals (CIs) for the association between daily snowfall and MI, adjusted for minimum daily temperatures. RESULTS: In all, 128 073 individual hospital admissions and 68 155 deaths due to MI were included in the analyses. The likelihood of MI was increased the day after a snowfall among men but not among women. Compared with 0 cm, 20 cm of snowfall was associated with an OR of 1.16 for hospital admission (95% CI 1.11–1.21) and 1.34 for death (95% CI 1.26–1.42) due to MI the following day among men. Corresponding ORs among women were 1.01 (95% CI 0.95–1.07) and 1.04 (95% CI 0.96–1.13). Similar but smaller associations were observed for snowfall duration (0 h v. 24 h) and MI. INTERPRETATION: Both the quantity and duration of snowfall were associated with subsequent risk of hospital admission or death due to MI, driven primarily by an effect in men. These data have implications for public health initiatives in regions with snowstorms.

Elevated ambient temperatures and risk of neural tube defects

Objectives The association between ambient heat and neural tube defects has received limited attention, despite imminent climate warming this century. We sought to determine the relationship between elevated outdoor temperatures during neurogenesis and risk of neural tube defects. Methods We carried out a retrospective cohort study of 887 710 fetuses between 3 and 4 weeks postconception from the months of April through September for 1988–2012 in Quebec, Canada. The exposure was maximum daily temperature and the outcome presence of neural tube defects at delivery. We estimated prevalence ratios (PR) and 95% CIs for the association between maximum temperature and neural tube defects in log-binomial regression models adjusted for maternal characteristics. Results Relative to 20°C, exposure to temperatures of 30°C was associated with risk of neural tube defects on day 5 (PR 1.56, 95% CI 1.04 to 2.35) and day 6 (PR 1.49, 95% CI 1.00 to 2.21) of the 4th week postconception, during the time of neural tube closure. The trend was apparent for spina bifida and anencephalus/encephalocoele, the main subtypes of neural tube defects. Temperature during the 3rd week postconception was not associated with neural tube defects. Conclusions Elevated ambient temperatures may be weakly associated with risk of neural tube defects during tube closure.

Heat and pregnancy-related emergencies: Risk of placental abruption during hot weather

INTRODUCTION Outdoor heat increases the risk of preterm birth and stillbirth, but the association with placental abruption has not been studied. Placental abruption is a medical emergency associated with major morbidity and mortality in pregnancy. We determined the relationship between ambient temperature and risk of placental abruption in warm seasons. MATERIAL AND METHODS We performed a case-crossover analysis of 17,172 women whose pregnancies were complicated by placental abruption in Quebec, Canada from May to October 1989-2012. The main exposure measure was the maximum temperature reached during the week before abruption. We computed odds ratios (OR) and 95% confidence intervals (CI) for the association of temperature with placental abruption, adjusted for humidity and public holidays. We assessed whether associations were stronger preterm or at term, or varied with maternal age, parity, comorbidity and socioeconomic status. RESULTS Compared with 15°C, a maximum weekly temperature of 30°C was associated with 1.07 times the odds of abruption (95% CI 0.99-1.16). When the timing of abruption was examined, the associations were significantly stronger at term (OR 1.12, 95% CI 1.02-1.24) than preterm (OR 0.96, 95% CI 0.83-1.10). Relationships were more prominent at term for women who were younger than 35years old, nulliparous or socioeconomically disadvantaged, but did not vary with comorbidity. Associations were stronger within 1 and 5days of abruption. Temperature was not associated with preterm abruption regardless of maternal characteristics. CONCLUSIONS Elevated temperatures in warm seasons may increase the risk of abruption in women whose pregnancies are near or at term. Pregnant women may be more sensitive to heat and should consider preventive measures such as air conditioning and hydration during hot weather.

Risk of hospitalization for fire-related burns during extreme cold weather

Background Environmental factors are important predictors of fires, but no study has examined the association between outdoor temperature and fire‐related burn injuries. We sought to investigate the relationship between extremely cold outdoor temperatures and the risk of hospitalization for fire‐related burns. Material and methods We carried out a time‐stratified case‐crossover study of 2470 patients hospitalized for fire‐related burn injuries during cold months between 1989 and 2014 in Quebec, Canada. The main exposure was the minimum outdoor temperature on the day of and the day before the burn. We computed odds ratios (OR) and 95% confidence intervals (CI) to evaluate the relationship between minimum temperature and fire‐related burns, and assessed how associations varied across sex and age. Results Exposure to extreme cold temperature was associated with a significantly higher risk of hospitalization for fire‐related burns. Compared with 0 °C, exposure to a minimum temperature of −30 °C was associated with an OR of 1.51 (95% CI 1.22–1.87) for hospitalization for fire‐related burns. The associations were somewhat stronger for women, youth, and the elderly. Compared with 0 °C, a minimum temperature of −30 °C was associated with an OR for fire‐related burn hospitalization of 1.65 for women (95% CI 1.13–2.40), 1.60 for age < 25 years (95% CI 1.02–2.52), and 1.73 for age ≥ 65 years (95% CI 1.08–2.77). Discussion Extremely cold outdoor temperature is a risk factor for fire‐related burns. Measures to prevent fires should be implemented prior to the winter season, and enhanced during extreme cold. HighlightsRisk of burns during cold temperature has not been studied.We examined the association of cold temperature with risk of fire‐related burns.At −30 °C, the odds of burns was 1.5 times higher than at 0 °C.Associations were stronger for women, young people, and the elderly.Extremely cold temperature potentially increases the risk of fire‐related burns.

Association of elevated ambient temperature with death from cocaine overdose

BACKGROUND Ecologic data suggest that elevated outdoor temperature is correlated with mortality rates from cocaine overdose. Using non-aggregated death records, we studied the association of hot temperatures with risk of death from cocaine overdose. METHODS We carried out a case-crossover study of all deaths from cocaine or other drug overdose between the months of May and September, from 2000 through 2013 in Quebec, Canada. We used conditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between maximum outdoor temperature and death from cocaine or other drug overdose. The main outcome measure was death from cocaine overdose as a function of maximum temperature the day of death and the days immediately preceding death. RESULTS There were 316 deaths from cocaine overdose and 446 from other drug overdoses during the study. Elevated temperature the preceding week was associated with the likelihood of death from cocaine but not other drug overdose. Compared with 20°C, a maximum weekly temperature of 30°C was associated with an OR of 2.07 for death from cocaine overdose (95% CI 1.15-3.73), but an OR of 1.03 for other drug overdoses (95% CI 0.60-1.75). Associations for cocaine overdose were present with maximum daily temperature the day of and each of the three days preceding death. CONCLUSIONS Elevated ambient temperature is associated with the risk of death from cocaine overdose. Public health practitioners and drug users should be aware of the added risk of mortality when cocaine is used during hot days.

Abortion and Infant Mortality on the First Day of Life

Background: Fetal imaging for congenital anomalies increases pregnancy terminations late in gestation. Objectives: We assessed whether late-pregnancy terminations can accidentally result in live births, and how these births impact infant mortality rates over time. Methods: We carried out a population-level analysis of 12,141 infant deaths in Quebec, Canada from 1986 to 2012. We calculated the proportion of infants born alive who died following pregnancy termination. The exposure was pregnancy termination with or without congenital anomaly recorded on death certificates. The main outcome was mortality on the first day of life by the hour. Results: Pregnancy termination was the cause of 19.4 infant deaths per 100,000 in 2000-2012, compared with 1.0 per 100,000 in 1986-1999. Most deaths after termination occurred in the first 3 h of life among infants with anomalies who weighed <500 g. In 2000-2012, infants who died following pregnancy termination led to an excess of 0.2 deaths per 1,000 on the first day of life, i.e. an 8.6% increase in the infant mortality rate (p value = 0.002). Conclusions: Pregnancy termination in mid-gestation carries the risk of accidental live birth. These neonates increasingly affect infant mortality rates. Better recording is needed, including data on the prevention and management of accidental live births after pregnancy termination.

Long-Term Risk of Cardiovascular Disease in Women Who Have Had Infants With Heart Defects

Background: The possibility that congenital heart defects signal a familial predisposition to cardiovascular disease has not been investigated. We aimed to determine whether the risk of cardiovascular disorders later in life was higher for women who have had newborns with congenital heart defects. Methods: We studied a cohort of 1 084 251 women who had delivered infants between 1989 and 2013 in Quebec, Canada. We identified women whose infants had critical, noncritical, or no heart defects, and tracked the women over time for future hospitalizations for cardiovascular disease, with follow-up extending up to 25 years past pregnancy. We calculated the incidence of cardiovascular hospitalization per 1000 person-years, and used Cox proportional hazards regression to estimate hazard ratios and 95% confidence intervals (CIs) for the association between infant heart defects and risk of maternal cardiovascular hospitalization. Models were adjusted for age, parity, preeclampsia, comorbidity, material deprivation, and time period. Results: Women whose infants had heart defects had a higher overall incidence of cardiovascular hospitalization. There were 3.38 cardiovascular hospitalizations per 1000 person-years for those with critical defects (95% CI, 2.67–4.27), 3.19 for noncritical defects (95% CI, 2.96–3.45), and 2.42 for no heart defects (95% CI, 2.39–2.44). In comparison with no heart defects, women whose infants had critical defects had a hazard ratio of 1.43 (95% CI, 1.13–1.82) for any cardiovascular hospitalization, and women whose infants had noncritical defects had a hazard ratio of 1.24 (95% CI, 1.15–1.34), in adjusted models. Risks of specific causes of cardiovascular hospitalization, including myocardial infarction, heart failure, and other atherosclerotic disorders, were also greater for mothers of infants with congenital heart defects than with no defects. Conclusions: Women whose infants have congenital heart defects have a greater risk of cardiovascular hospitalization later in life. Congenital heart defects in offspring may be an early marker of predisposition to cardiovascular disease.

Ambient Temperature and Risk of Preeclampsia: Biased Association?

BACKGROUND Preeclampsia is associated with conception during warm months and delivery during cold months. We sought to determine whether season of conception and shorter gestation bias the associations. METHODS We used hospital discharge summaries to identify 65 273 pregnancies with and 1 825 438 without preeclampsia in Quebec, Canada between 1989 and 2012. We obtained data on mean temperature for the month following conception and the month before hospital admission. We used cubic splines in log-binomial models to estimate the association between temperature and preeclampsia (risk ratios, RR; 95% confidence interval, CI). To assess the potential for bias, we compared models progressively adjusted for baseline maternal characteristics, season of conception, and length of gestation at admission. RESULTS With adjustment for baseline maternal characteristics only, risk of preeclampsia was higher for hot temperatures at conception and cold temperatures at end of pregnancy. Adjusting for season at conception removed the association between preeclampsia and temperature at conception. Adjustment for length of gestation removed the association between preeclampsia and temperature at end of pregnancy. CONCLUSIONS This study demonstrates that associations between ambient temperature and preeclampsia may be biased by short gestation, because preeclampsia commonly occurs earlier in pregnancy. Temperatures during gestation change with time for all women, and temperatures early in pregnancy frequently differ from temperatures later in pregnancy. Variation in temperature over gestation may lead to a coincidental association with preeclampsia.