title: The Relationship Between Apparent Temperature and Daily Number of Live Births in Montreal.
abstract: OBJECTIVE
  Temperature is a hypothesized determinant of early delivery, but seasonal and long term trends, delayed effects of temperature, and the influence of extreme cold temperatures have not yet been addressed. We aim to study the influence of apparent temperature on daily number of births, considering lag structures, seasonality and long term trends.
  
  
  METHODS
  We used daily number of births in conjunction with apparent outdoor temperatures between 1981 and 2010 in Montreal. We used Poisson regression combined with a distributed lag nonlinear model to consider non-linear relationships between temperature and daily number of births across specific lag periods.
  
  
  RESULTS
  We found that apparent temperature was associated with the daily number of births in Montreal, with a 1-day delay. We found an increase in births on hot days, and decrease on cold days, both offset by a harvesting effect after 4 and 5 days.
  
  
  CONCLUSIONS
  This study suggests that the number of births is affected by extreme temperatures. Obstetric and perinatal service providers should be prepared for spikes in the number of births caused by extreme temperatures.
authors.affiliation: Institute for Health and Social Policy, McGill University, Meredith, Charles, House, 1130 Pine Avenue West, Montreal, QC, H3A 1A3, Canada. tarik.benmarhnia@mcgill.ca.
authors.forename: Tarik
authors.initials: T
authors.lastname: Benmarhnia
authors.affiliation: Institut National de Santé Publique du Québec, Montreal, QC, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Auger
authors.affiliation: Institut National de Santé Publique du Québec, Montreal, QC, Canada.
authors.forename: Virginie
authors.initials: V
authors.lastname: Stanislas
authors.affiliation: Institut National de Santé Publique du Québec, Montreal, QC, Canada.
authors.forename: Ernest
authors.initials: E
authors.lastname: Lo
authors.affiliation: Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, QC, Canada.
authors.forename: Jay S
authors.initials: JS
authors.lastname: Kaufman
mesh_terms: D003080:Cold Temperature / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*; D011792:Quebec; D012621:Seasons
keywords: Apparent temperature; Obstetric and pediatric health planning; Time series analysis; Weather