title: Birth weight and risk of early-onset breast cancer (Denmark).
abstract: OBJECTIVE
  To investigate if birth weight is associated with early-onset breast cancer. The mechanism behind an association with high birth weight could be the link between fetal growth and estrogens in utero.
  
  
  METHODS
  We conducted a population-based case-control study in Denmark including 881 women with breast cancer diagnosed before the age of 40 years and 3,423 age-matched controls. Information concerning birth weight and other birth-related variables was obtained from midwife reports.
  
  
  RESULTS
  The risk of early-onset breast cancer was increased 1.25 times (95% CI 1.00-2.51) for birth weights above 4,000 g and 1.59 times (95% CI 1.00-1.55) for birth weights below 2,500 g in comparison with birthweights of 3,000-3,499 g.
  
  
  CONCLUSIONS
  The finding that high birth weight is associated with breast cancer is compatible with the hypothesis that level of estrogen during pregnancy is related to breast cancer in early adult life. The finding that low birth weight is also associated with breast cancer may indicate that other characteristics of the fetal environment may be important for breast cancer in early adult life.
authors.affiliation: Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark. lene@cancer.dk
authors.forename: Lene
authors.initials: L
authors.lastname: Mellemkjaer
authors.forename: Mette Lena
authors.initials: ML
authors.lastname: Olsen
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
authors.forename: Ane Marie
authors.initials: AM
authors.lastname: Thulstrup
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Olsen
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D001724:Birth Weight / Q000502:physiology*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000503:physiopathology; D016022:Case-Control Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008875:Middle Aged; D011159:Population Surveillance; D012306:Risk