title: Impact of gender, maternal education, and birth order on the development of language comprehension:  a longitudinal study from 18 to 36 months of age.
abstract: OBJECTIVE
  To investigate the impact of child gender, maternal education, and birth order on language comprehension (LC) status at 18 and 36 months of age and on the change in LC between these time points. Gender interactions and interactions between maternal education and birth order are also examined.
  
  
  METHODS
  This study is based on data from the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health. Maternal report data on education, birth order, and child language in a sample of 44,921 children were used in linear regression analyses.
  
  
  RESULTS
  At 18 and 36 months of age, first-born girls of mothers with high educational attainment had the highest level of LC. Between 18 and 36 months of age, first-born boys of mothers with high educational attainment had the highest increase in LC. Having a highly educated mother contributed more to the increase in LC in boys than in girls. The boys whose mothers had the highest education level had lower scores than the girls whose mothers had the lowest educational level, at both ages. Although significant, the considerable effect of high maternal education was not substantially dependent on birth-order status.
  
  
  CONCLUSIONS
  Boys develop LC at a faster rate than girls between 18 and 36 months, but girls still remain superior in their level of LC at 36 months of age. Being firstborn or having a highly educated mother does not compensate for this lag.
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Oslo, Norway. imac.maria.zambrana@fhi.no
authors.forename: Imac Maria
authors.initials: IM
authors.lastname: Zambrana
authors.forename: Eivind
authors.initials: E
authors.lastname: Ystrom
authors.forename: Francisco
authors.initials: F
authors.lastname: Pons
mesh_terms: D000367:Age Factors; D001722:Birth Order / Q000523:psychology*; D002675:Child, Preschool; D032882:Comprehension / Q000502:physiology*; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007802:Language; D007804:Language Development; D008137:Longitudinal Studies; D008297:Male; D009035:Mothers / Q000193:education; D009664:Norway / Q000453:epidemiology; D012737:Sex Factors; D011795:Surveys and Questionnaires