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Table 1 Covariates in relation to immigration status in controls and in relation to the risk of childhood autism

From: The risk of childhood autism among second-generation migrants in Finland: a case–control study

  Immigration   Relationship between covariates and childhood autism p-valuea
Covariates Both parents Finnish n (%) Mother only immigrated n (%) Father only immigrated n (%) Both parents immigrated n (%) p-valuea  
Maternal age (≥median, 29 years) 2 386 (55.9) 48 (60.0) 48 (62.3) 34 (36.6) 0.001 <0.001
 mean (years) 29.5 30.3 30.1 27.4   
 SD (years) 5.3 5.2 5.2 4.7   
Paternal age (≥median, 32 years) 2 055 (48.2) 47 (58.8) 41 (53.3) 58 (62.4) 0.01 0.003
 mean (years) 31.9 35.7 32.6 33.0   
 SD (years) 5.9 7.7 6.7 5.8   
Smokingb 714 (17.2) 10 (13.2) 10 (13.2) 1 (1.2) <0.001 0.77
Previous births (≥2) 1 105 (25.9) 15 (18.8) 18 (23.4) 36 (38.7) 0.02 0.22
Pre-term birth (<37 weeks) 229 (5.4) 8 (10.0) 1 (1.3) 7 (7.5) 0.08 0.06
Low birthweight (<2500 g) 135 (3.2) 3 (3.8) 0 (0) 3 (3.2) 0.45 <0.001
 mean (g) 3598 3558 3580 3539   
 SD (g) 546 450 490 529   
  1. aX2 test, bfrequency missing = 47 cases, 132 controls. OR=odds ratio, CI=confidence interval.