title: Two-Year Comparison of Growth Indices of Twins with Dissimilar Weight at Birth (Low Birth Weight vs. Normal Twin).
abstract: BACKGROUND
  Twin pregnancies are commonly associated with low birth weight (LBW) infants. Most studies focus on growth of LBW compared with normal infants in singleton. However, there has not been any study on twins to compare LBW with normal birth weight (NBW) infants as a match control of the same twin.
  
  
  METHODS
  This cohort study was conducted at Healthcare centers of Kashan, in 2013. Twins differing in birth weight (one with LBW and the other with NBW) were assessed using the care charts in Well Care program in regard to weight, height and head circumference measurements at birth and after 6, 12, 24 months of age and were compared separately between all matched pairs and in four sex-twin subgroups which was defined according to the sex of each twin in pairs; SF (Same-sex: Female), SM (Same-sex: Male), LF (LBW: Female) and LM (LBW: Male).
  
  
  RESULTS
  Incidence of dissimilar twins in birth weight was 28.4%. The weight of LBW was significantly lower than the NBW cohort in SF and LF subgroups up to 24 months. The height of LBW was not significantly different from NBW cohort in SM and LM subgroups up to 24 month. Head circumference was significantly higher in LBW compared to NBW cohort in LM subgroup up to 24 month. However, these indices were significantly lower in LBW compared to NBW cohort in all pairs.
  
  
  CONCLUSIONS
  Although LBW cohort was significantly lower than the NBW in growth indices at birth to 2 years old in all twins, however, highly variable results was observed in four subgroups of sex-twin.
authors.affiliation: Dept. of Biostatistics & Epidemiology, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Atoof
authors.affiliation: Dept. of Biostatistics & Epidemiology, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Eshraghian
authors.affiliation: Dept. of Biostatistics & Epidemiology, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Kazem
authors.initials: K
authors.lastname: Mohammad
authors.affiliation: Social Determinants of Health Research Center, Dept. of Community Medicine, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Moravveji
authors.affiliation: Dept. of Pediatrics, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Sharif
authors.affiliation: Dept. of Biostatistics & Epidemiology, Faculty of Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Mahmoodi
keywords: Growth indicator; Low birth weight; Twins