title: Seasonality of infant feeding practices in three Brazilian birth cohorts.
abstract: BACKGROUND
  We assessed the influence of season of birth on duration of breastfeeding and other feeding patterns in three population-based birth cohort studies in the city of Pelotas, Southern Brazil.
  
  
  METHODS
  In 1982, 1993 and 2004, all hospital-born children in the city were enrolled in three cohort studies (n = 5914, 5249 and 4287, respectively). Children and their mothers were periodically visited in the first 2 years of life, to collect information on the duration of breastfeeding and the ages at which different types of foods were introduced on a regular basis. Two independent variables were studied: month of birth and mean environmental temperature in the first month of life. Survival analyses and chi-squared tests were used to evaluate the associations. Temperature-based slope indices of inequality were also calculated.
  
  
  RESULTS
  Duration of breastfeeding was lower among children born from April to June (months preceding winter) and spending their first month of life in colder temperatures. The influence of season of birth on breastfeeding patterns and the introduction of cow's milk differed according to maternal education, with the strongest effects among children belonging to less educated mothers. Early introduction of fruits (1982 and 1993 cohorts) and vegetables (1982 cohort) were also associated with lower environmental temperature in the first month of life, but not with trimester of birth.
  
  
  CONCLUSIONS
  Colder temperatures adversely affect duration of breastfeeding and feeding patterns in infancy, especially among the poorest. This finding should be considered in breastfeeding promotion programmes.
authors.affiliation: Post-graduate Program in Nutrition, Federal University of Santa Catarina, Florianópolis, SC, Brazil. david.epidemio@gmail.com
authors.forename: David A
authors.initials: DA
authors.lastname: González-Chica
authors.forename: Helen
authors.initials: H
authors.lastname: Gonçalves
authors.forename: Aydin
authors.initials: A
authors.lastname: Nazmi
authors.forename: Iná S
authors.initials: IS
authors.lastname: Santos
authors.forename: Aluísio J D
authors.initials: AJ
authors.lastname: Barros
authors.forename: Alicia
authors.initials: A
authors.lastname: Matijasevich
authors.forename: Cesar G
authors.initials: CG
authors.lastname: Victora
mesh_terms: D001903:Bottle Feeding / Q000706:statistics & numerical data; D001938:Brazil / Q000453:epidemiology; D001942:Breast Feeding / Q000706:statistics & numerical data*; D004522:Educational Status; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D012621:Seasons; D013696:Temperature; D013997:Time Factors