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Table 1 Characteristics of the study population (n = 1163)

From: Use of hormonal contraceptives and occurrence of pregnancy-related pelvic pain: a prospective cohort study in Norway

  Study cohort Number (%) Used hormonal contraceptives before first birth  
   % p value
Age    
   35–36 years 320 (15.4) 49.1  
   37–38 years 273 (13.1) 49.5  
   39–40 years 276 (13.3) 42.4  
   41–42 years 296 (14.2 27.4  
   43–44 years 260 (12.5) 20.4  
   45–46 years 296 (14.2) 15.5  
   4949 years 357 (17.2) 10.9 p < 0.0001
Age at menarche    
   < = 12 year 538 (26.4) 30.1  
   13 years 615 (30.2) 35.5  
   > = 14 years 882 (43.3) 26.6 p = 0.001
Age at first birth    
   <= 20 years 503 (24.2) 6.4  
   21–25 years 961 (46.3) 25.6  
   > = 26 years 614 (29.5) 57.0 p<= 0.0001
Weight of newborn child    
   -3000 g 360 (18.0) 31.4  
   30001–3500 g 750 (37.4) 31.2  
   3501–4000 g 617 (30.8) 28.4  
   > = 4001 g 276 (13.8) 31.9 P = 0.6
Education    
   7–9 years 428 (20.9) 12.9  
   10–12 years 759 (37.2) 24.2  
   13–15 years 517 (25.3) 39.9  
   > = 16 years 339 (16.6) 51.9 p < 0.0001
Years between menarche and first birth    
   0–5 years 215(10.6) 5.6  
   6–10 years 926(45.5) 17.4  
   11–15 years 628 (30.9) 43.0  
   > = 16 years 266 (13.1) 64.7 p < 0.0001
Number of births    
   One 307(14.8) 46.3  
   Two 1044 (50.2) 32.2  
   Three 543 (26.1) 23.9  
   > = Four 184(8.9) 10.9 p < 0.0001
Smoking in the first pregnancy    
   No 1396 (69.6) 30.5  
   Yes 611 (30.4) 30.0 p = 0.8