title: Effects of infants' birth order, maternal age, and socio-economic status on birth weight.
abstract: OBJECTIVE
  To determine the effects of infants' birth order, maternal age, and socioeconomic status (SES) on birth weight.
  
  
  METHODS
  This cross-sectional study included a sample of 858 mothers recruited over a 6-month period in 2010, in a defined population of 9 urban health centers, and who were admitted for their infants' first vaccination. Maternal clinical data, demographic data, and infants' birth weight were obtained from the interview and maternal hospital files. Multiple regression and analysis of variance were used for data analysis.
  
  
  RESULTS
  First and fourth births had lower birth weights compared with second and third births in all maternal ages in controlling parity, birth weight increases with maternal age up to the early 24, and then tends to level off. Male gender, maternal age 20-24 years, second and third births had a significant positive effect on birth weight. Lower family economic status and higher educational attainment were significantly associated with lower birth weight. For women in the 15-19 and 40-44 years age groups, the second birth order was associated with the most undesirable effect on birth weight.
  
  
  CONCLUSIONS
  Accessibility of health care services, parity, maternal age, and socioeconomic factors are strongly associated with infants' birth weight.
authors.affiliation: Student Research Committee, School of Nutrition, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Seyed J
authors.initials: SJ
authors.lastname: Ghaemmaghami
authors.forename: Leila
authors.initials: L
authors.lastname: Nikniaz
authors.forename: Reza
authors.initials: R
authors.lastname: Mahdavi
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Nikniaz
authors.forename: Farzad
authors.initials: F
authors.lastname: Razmifard
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Afsharnia
mesh_terms: D000328:Adult; D001722:Birth Order; D001724:Birth Weight; D005260:Female; D006801:Humans; D007223:Infant; D008423:Maternal Age; D011247:Pregnancy; D012923:Social Class