title: Risks for low intellectual performance related to being born small for gestational age are modified by gestational age.
abstract: OBJECTIVE
  We sought to study whether the association between being born small for gestational age and risk for low intellectual performance was modified by gestational age.
  
  
  METHODS
  A population-based cohort study was conducted of 352,125 boys who were born between 28 and 43 completed weeks of gestation from 1973 to 1981 in Sweden. Risk for low intellectual performance at military conscription, estimated as odds ratios with 95% confidence intervals was measured.
  
  
  RESULTS
  Compared with men who were born preterm (28-36 weeks) and had normal birth weight for gestational age, men who were born preterm and had a very low birth weight for gestational age were not at increased risk for low intellectual performance. In contrast, men who were born preterm with a very short birth length or a very small head circumference for gestational age faced a near doubled risk for low intellectual performance compared with their appropriate peers. Among men who were born at term (37-41 weeks), risk for low intellectual performance was increased among those with very or moderately small birth weight, birth length, or head circumference for gestational age.
  
  
  CONCLUSIONS
  During early stages of gestation, growth in length and head circumference may be more important for intellectual development than weight increase. Future studies on size at birth and intellectual performance should consider also including anthropometric measurements other than birth weight.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, SE-171 77 Stockholm, Sweden. niklas.bergvall@meb.ki.se
authors.forename: Niklas
authors.initials: N
authors.lastname: Bergvall
authors.forename: Anastasia
authors.initials: A
authors.lastname: Iliadou
authors.forename: Stefan
authors.initials: S
authors.lastname: Johansson
authors.forename: Torsten
authors.initials: T
authors.lastname: Tuvemo
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D000293:Adolescent; D001724:Birth Weight; D001827:Body Height; D002508:Cephalometry; D015331:Cohort Studies; D005317:Fetal Growth Retardation; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male