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Table 1 Background characteristics of primiparous women aged 25–31 years (reference group) and ≥32 years (advanced age), and for representativeness; comparisons between a sub-sample giving birth in 2003 and all primiparous women aged >25 years in Norway in 2003 (P-value for differences between a sub-sample from 2003 and all Norwegian primiparous women >25 years giving birth in 2003)

From: Experience of childbirth in first-time mothers of advanced age – a Norwegian population-based study

  Women in the study Women ≥ 25 years giving birth in 2003
Age 25-31 Age ≥32 All Sub sample Norway  
n=21 226 n=8839 n=30 065 n=3549 n=16 760  
% % % % % P-value
Demographic and social factors       
Age (years)*       0.07
  25-29    50.8 55.2 54.0  
  30-34    37.6 35.2 35.1  
  35-39    10.3 8.8 9.6  
  ≥40    1.3 0.8 1.2  
Smoking* 8.4 7.6 8.2 10.8 13.9 <0.001
Single status 2.9 4.9 3.5 2.7 5.7 <0.001
Native language other than Norwegian 5.9 8 6.5 4.7   
Unemployed 1.7 1.6 1.7    
Income (NOR)**       
  <200 000 11.2 6 8.7    
  200 000–399 999 55.5 43.7 51.5    
  ≥400 000 29.1 46 33.7    
Pregravid BMI, mean (kg/m2) 23.6 24.1 23.8    
IVF present pregnancy* 2.6 8.9 4.4 3.8 4.9 <0.001
Labour*       
Mode of delivery       
  Vacuum 14.2 16 14.8 14.1 13.7 0.54
  Forceps 2.8 3.4 3 2.7 2.4 0.27
  Elective cesarean delivery 3.1 6 4 3.8 5.3 <0.001
  Emergency cesarian delivery 9.7 13.5 10.8 11.4 12.5 0.06
  Unspecified cesarean delivery 1.9 2.9 2.2 1.2 2.5 <0.001
Prematurity** 5.5 6.4 5.8 6.5 8.8 <0.001
Neonatal Transfer 9.2 10.8 9.3 10.8 12.5 <0.001
  1. *Data from the Norwegian Medical birth Register.
  2. **NKR: NOK/GBP=10.90.
  3. ***Prematurity: 22–36 weeks of pregnancy.