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Table 1 Comparison of age at menarche and reproductive factors between BRCA2-positive cases, BRCA2-negative cases and controls

From: BRCA2mutation carriers, reproductive factors and breast cancer risk

  BRCA2-positive cases (n = 100) BRCA2-negative cases (n = 361) Matched controls (n = 1000)
Risk factor % distribution Mean % distribution Mean % distribution Mean
Age at menarche n = 85 (85%)*   n = 313 (87%)*   n = 860 (86%)*  
   < 13 years 25.9 13.2 years 31.3 13.1 years 27.4 13.3 years
   13 years 35.3   29.1   28.9  
   > 13 years 38.8   39.6   43.6  
Parous n = 99 (99%)   n = 355 (98%)   n = 991 (99%)  
   Yes 89.9   88.2   93.0  
   No 10.0   11.8   7.0  
Parous women       
Age at first birth n = 85 (96%)   n = 300 (96%)   n = 880 (95%)  
   < 20 years 16.5 22.2 years 22.3 23.0 years 25.0 22.3 years
   20–29 years 80.0   69.3   69.6  
   > 29 years 3.5   8.3   5.4  
Number of births n = 89 (100%)   n = 313 (100%)   n = 922 (100%)  
   1–2 32.6 3.3 births 40.9 3.0 births 39.7 3.2 births
   3–4 46.1   45.7   42.5  
   5+ 21.3   13.4   17.8  
Total duration of breastfeeding n = 58 (65%)   n = 209 (67%)   n = 640 (69%)  
   0 months 1.7 8.5 months 2.9 9.2 months 1.9 9.3 months
   < 1 months 1.7   5.3   6.9  
   1–6 months 44.8   37.3   38.4  
   7–12 months 29.3   31.1   28.8  
   13–24 months 19.0   18.7   17.2  
   > 24 months 3.4   4.8   6.9  
  1. *Percentages with recorded responses for each item.
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