title: Extremely preterm birth affects boys more and socio-economic and neonatal variables pose sex-specific risks.
abstract: OBJECTIVE
  The early identification of at-risk extremely preterm (EPT) children could improve long-term outcomes. This study sought to investigate sex differences in developmental outcomes and to identify sex-specific predictors at two and a half years of age.
  
  
  METHODS
  We assessed 217 boys and 181 girls born before 27-week gestation using the Bayley Scales of Infant and Toddler Development, third edition (Bayley-III), as a part of the Extremely Preterm Infants in Sweden Study. Sex-specific differences were calculated. Socio-economic, birth and neonatal factors were calculated separately for boys and girls using regression models.
  
  
  RESULTS
  Girls scored significantly higher than boys on all Bayley-III indices. In both sexes, brain injury, long-term ventilator treatment and foreign-born mothers predicted lower scores. Receiving breast milk by hospital discharge predicted higher scores. Severe retinopathy of prematurity was the strongest predictor of cognitive and language deficits in boys. High parental education predicted higher cognitive and language scores in girls, whereas severe bronchopulmonary dysplasia was the strongest predictor of motor deficits.
  
  
  CONCLUSIONS
  Extreme prematurity seems to affect boys more than girls. Socio-economic and neonatal factors confer similar risks or protections on both sexes, but some variables pose sex-specific risks. An awareness of risk factors may provide the basis for treatment and follow-up guidelines.
authors.affiliation: Department of Psychology, Lund University, Lund, Sweden.
authors.forename: Johanna
authors.initials: J
authors.lastname: Månsson
authors.forename: Vineta
authors.initials: V
authors.lastname: Fellman
authors.forename: Karin
authors.initials: K
authors.lastname: Stjernqvist
mesh_terms: D002675:Child, Preschool; D003071:Cognition; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D062071:Infant, Extremely Premature / Q000254:growth & development*; D007231:Infant, Newborn; D007804:Language Development; D008297:Male; D009048:Motor Skills; D012307:Risk Factors; D012727:Sex Characteristics; D012959:Socioeconomic Factors
keywords: Bayley Scales of Infant and Toddler Development third edition; Developmental outcome; Extremely Preterm Infants in Sweden Study; Extremely preterm; Sex differences