title: Exposure to low outdoor temperature in the midtrimester is associated with low birth weight.
abstract: BACKGROUND
  Although seasonal variation of birth weight has been reported previously, contributing factors such as the meteorological factor and its specific period of exposure remain unclear.
  
  
  OBJECTIVE
  To investigate the effect of season on birth weight and to determine the meteorological factor and its specific period of exposure which can contribute to any seasonal variation in birth weight.
  
  
  METHODS
  Retrospective analysis of 3333 singleton live births after 36 completed weeks of pregnancy. Maternal age, parity, route of delivery, sex and individual meteorological variables for the first, second, and third trimesters of each pregnancy were analysed using multiple regression analysis with the birth weight as the dependent variable.
  
  
  RESULTS
  A seasonal pattern was observed with lowest birth weights in women who had their last menstrual periods in summer and autumn. Upon multiple regression analysis, sex, parity, mode of delivery, and the temperature which the mother was exposed to in the second trimester were the independent determinants of birth weight.
  
  
  CONCLUSIONS
  Exposure to low outdoor ambient temperature in the midtrimester can be associated with low birth weight.
authors.affiliation: Department of Obstetrics and Gynecology, Marmara University School of Medicine, Istanbul, Turkey.
authors.forename: Koray
authors.initials: K
authors.lastname: Elter
authors.forename: Emine
authors.initials: E
authors.lastname: Ay
authors.forename: Esra
authors.initials: E
authors.lastname: Uyar
authors.forename: Zehra N
authors.initials: ZN
authors.lastname: Kavak
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D015331:Cohort Studies; D003080:Cold Temperature / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D018811:Maternal Exposure; D015999:Multivariate Analysis; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011336:Probability; D012044:Regression Analysis; D012189:Retrospective Studies; D018570:Risk Assessment; D012621:Seasons