title: Ambient temperature and congenital heart defects.
abstract: OBJECTIVE
  Does maternal exposure during pregnancy to higher ambient temperature increase the risk of congenital heart defects (CHDs)?
  
  
  CONCLUSIONS
  Significant associations were found between maternal exposure during pregnancy to higher ambient temperature and CHDs risk especially during the cold season.
  
  
  BACKGROUND
  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.
  
  
  METHODS
  This population registry-based cohort study included 135 527 live and stillbirths in the Tel-Aviv region of Israel in 2000-2006.
  
  
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  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.
authors.affiliation: School of Public Health, Faculty of Social Welfare and Health Sciences, University of Haifa, Mount Carmel, Haifa 31905, Israel. kagayshay@gmail.com
authors.forename: K
authors.initials: K
authors.lastname: Agay-Shay
authors.forename: M
authors.initials: M
authors.lastname: Friger
authors.forename: S
authors.initials: S
authors.lastname: Linn
authors.forename: A
authors.initials: A
authors.lastname: Peled
authors.forename: Y
authors.initials: Y
authors.lastname: Amitai
authors.forename: C
authors.initials: C
authors.lastname: Peretz
mesh_terms: D005260:Female; D006330:Heart Defects, Congenital / Q000209:etiology*; D006801:Humans; D016017:Odds Ratio; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011297:Prenatal Exposure Delayed Effects; D012189:Retrospective Studies; D018570:Risk Assessment; D013696:Temperature
keywords: birth defects; congenital heart defects; congenital malformation; heat wave; temperature