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Table 1 Comparability of the intervention and control groups, % if not otherwise indicated1)

From: Special features of health services and register based trials – experiences from a randomized trial of childbirth classes

  Intervention Control
  (n = 845) (n = 723)
Age at birth, mean (SD) 30.6 (5.5) 30.6 (5.4)
   < 25 yr 14 13
   25–29 28 30
   30–34 30 31
   35 + 27 27
Marital status   
   Married 52 59
   Common law 38 35
   Other + NG 10 6
Social class   
   Upper white collar 27 29
   Lower white collar 31 29
   Worker 10 9
   Student 13 12
   Other + NG 20 20
Previous births2), mean (SD) 0.67 (0.97) 0.70 (0.98)
   0 57 55
Previous pregnancies2), mean (SD) 1.07 (1.27) 1.16 (1.32)
Smoking2)   
   No 84 85
   Current 14 13
   Quitted (during pregnancy) 2 2
Timing of 1st prenatal visit, mean (SD) 9.0 (3.1) 9.0 (3.1)
   < 10 gest. weeks 69 68
Boy 53 52
Twin 1 1
Pregnancy length, mean weeks (SD) 40.1 (1.6) 40.0 (1.6)
   < 37 3 3
   37–41.9 89 91
   42+ 8 6
Birth weight, mean g (SD) 3521 (487) 3522 (537)
   < 2500 3 4
   2500–2999 9 9
   3000–3499 35 33
   3500–3999 40 36
   4000+ 13 18
  1. 1) NG = no information
  2. 2) Missing information 0–4 women in each group