title: Birthweight differences between USA and China and their relevance to breast cancer aetiology.
abstract: BACKGROUND
  There has been renewed interest about determinants of birth size following the propagation of hypotheses that birth size parameters may have long-term consequences on the occurrence of common diseases in adulthood, including breast cancer.
  
  
  METHODS
  In the context of a cohort study, 296 Caucasian pregnant women in Boston, USA and 329 Chinese pregnant women in Shanghai, China were followed to term. Birth size characteristics of the baby and maternal anthropometry were measured using standardized protocols. Analyses were conducted through multiple regression procedures.
  
  
  RESULTS
  No significant difference was found between US and Chinese newborns with respect to gestational age. Among US women, pregravid oral contraceptive use was strongly associated with higher birthweight. In both US and Chinese women, birthweight was positively associated with height, pre-pregnancy body mass index, and weight gain during pregnancy. More importantly, the difference in these three maternal variables between the two samples fully explains the birthweight difference between the two populations.
  
  
  CONCLUSIONS
  We postulate that babies in China may have lower birthweight because their mothers' anthropometry imposes constraints on the growth of the fetus. When Chinese women migrate to the US, they tend to grow taller and heavier so that their babies can reach, on the average, a higher birthweight. The recurrence of this process in successive generations could explain why eventually Chinese Americans tend to have comparable birth and adult anthropometric characteristics, as well as comparable breast cancer rates, to those of Caucasian Americans.
authors.affiliation: Department of Hygiene and Epidemiology, School of Medicine, University of Athens, Greece.
authors.forename: Pagona
authors.initials: P
authors.lastname: Lagiou
authors.forename: Chung-Cheng
authors.initials: CC
authors.lastname: Hsieh
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Trichopoulos
authors.forename: Biao
authors.initials: B
authors.lastname: Xu
authors.forename: Joanne
authors.initials: J
authors.lastname: Wuu
authors.forename: Lorelei
authors.initials: L
authors.lastname: Mucci
authors.forename: Rulla
authors.initials: R
authors.lastname: Tamimi
authors.forename: Hans-Olov
authors.initials: HO
authors.lastname: Adami
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight / Q000502:physiology*; D001827:Body Height; D015992:Body Mass Index; D001900:Boston / Q000453:epidemiology; D001943:Breast Neoplasms / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology*; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000502:physiology* / Q000706:statistics & numerical data; D015430:Weight Gain / Q000502:physiology