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Table 1 Comparisons of the characteristics of the enrolled children and mothers in the case and control groups

From: Associations among maternal pre-pregnancy body mass index, gestational weight gain and risk of autism in the Han Chinese population

  Control Case t/χ2 df p
(N = 2200) (N = 697)
1. Child age (years), mean (SD) 5.78 (2.36) 5.04 (1.08) 11.457 2552b <0.001
2. Paternal age (years), mean (SD) 29.39 (4.48) 30.33 (4.30) −4.877 2895 <0.001
3. Maternal age (years), mean (SD) 27.06 (3.67) 27.94 (3.37) −5.890 1262b <0.001
4. Birth weight (kg), mean (SD) 3.35 (0.46) 3.38 (0.45) −1.527 2895 0.120
5. Child Sex, n (%)
 Male 1187 (54%) 599 (85.9%) 229.037 1 0.001
 Female 1013 (46%) 98 (14.1%)    
6. Family annual income (Yuan), n (%)
 low <50,000 347 (15.8%) 296 (42.5%) 274.318 2 <0.001
 medium 50,000–100,000 715 (32.5%) 246 (35.3%)    
 high >100,000 1138 (51.7%) 155 (22.2%)    
7. Maternal history of daily alcohol use, n (%)
 Yes 9 (0.41%) 4 (0.57%) 0.322 1 0.571
 No 2191 (99.59%) 693 (99.43%)    
8. Maternal history of drug use, n (%)a
 Yes 0 3 (0.43%) 0.014
 No 2200(100%) 694 (99.57%)    
  1. aFisher’s exact test was used
  2. bThe standard variance was not equal, approximate t-test was adapted and adjusted the df