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Table 1 Characteristics of the study population when the child is 6 months

From: Association between colic and sleep problems in infancy and subsequent development, emotional and behavioral problems: a longitudinal study

  n (%) mean (SD) Median (range)
Child (N= 86,724) mean (SD)
Male n (%) 40, 205 (51.0)   
Missing (n= 7947)    
Gestation age
 ≥37 weeks 70,815 (95.0)   
 32–36 weeks 3231 (4.3)   
 28–31 weeks 309 (0.4)   
  <  28 weeks 192 (0.3)   
Missing (n= 12,177)    
Birth weight in grams 78,816   3600 (500, 5960)
Missing (n = 7908)    
Mother (N= 86,724)
Maternal age 82,377 29.8 (4.5)  
Missing (n = 4387)    
Maternal education a
 low 26,607 (34.0)   
 medium 32,941 (42.0)   
 high 18,836 (24.0)   
Missing (n = 8340)    
Work status b    
 Education 4930 (6.0)   
 Employed 68,153 (83.1)   
 Other 8938 (10.9)   
Missing (n = 4703)    
Civil status c
 Married/co-habiting 80,333 (97.9)   
Missing (n = 4640)    
  1. a Education at 16–20 weeks of pregnancy: low education = completed elementary school and or high school. Medium education = completed college / university 1–3 years. High education = completed college / university 4 years
  2. b Work Status at 16–20 weeks of pregnancy: education = student, at home, trainee, military service. Employed = employed in the public or private sector. Other = unemployed
  3. c Civil status at 16–20 weeks of pregnancy