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Table 2 Risk of breast cancer associated with full-term pregnancies and breast feeding.

From: Variation in breast cancer risk associated with factors related to pregnancies according to truncating mutation location, in the French National BRCA1 and BRCA2 mutations carrier cohort (GENEPSO)

Reproductive Factors One woman per family cohort: 39,666 person-years of follow-up BRCA1mutation carriers: 25,045 person-years of follow-up BRCA2mutation carriers: 14,621 person-years of follow-up
   Person-yearsa No. of casesa HR 95% CI Pvalue Person-yearsa No. of casesa HR 95% CI Pvalue Person-yearsa No. of casesa HR 95% CI Pvalue
Parityb
  Nulliparous 25,333 58 1.00    16,215 38 1.00    9,118 20 1.00   
  Parous 14,333 321 0.77 0.53-1.13   8,830 202 0.76 0.49-1.19   5,503 119 0.78 0.39-1.55  
No. of full-term pregnanciesb
  0 25,333 58 1.00    16,215 38 1.00    9,118 20 1.00   
  1 4,435 90 1.10 0.72-1.68   2,777 58 1.04 0.63-1.72   1,658 32 1.24 0.59-2.61  
  2 5,640 138 0.79 0.52-1.20   3,540 87 0.81 0.50-1.30   2,100 51 0.73 0.35-1.55  
  ≥3 4,243 92 0.51 0.33-0.81 <10-3 2,498 56 0.52 0.31-0.89 0.02 1,745 36 0.49 0.22-1.10 0.08
  Trend    0.77 0.68-0.88 <10-3    0.78 0.67-0.91 <10-3    0.74 0.58-0.95 0.02
No. of full-term pregnancies by attained ageb
  0 25,333 58 1.00    16,215 38 1.00    9,118 20 1.00   
  1-2 before age 40 8,146 131 1.05 0.68-1.63   5,169 88 1.04 0.62-1.77   2,977 43 1.12 0.53-2.37  
  ≥3 before age 40 2,303 40 0.82 0.48-1.41   1,414 29 0.88 0.46-1.66   889 11 0.64 0.23-1.75  
  1-2 after age 40 1,929 97 0.70 0.36-1.36   1,148 57 0.70 0.32-1.50   781 40 0.61 0.19-1.99  
  ≥3 after age 40 1,940 52 0.35 0.17-0.70 <10-3 1,084 27 0.34 0.15-0.76 0.01 856 25 0.36 0.11-1.16 0.09
Age at first full-term pregnancyc
  < 20 years 1,866 39 1.00    1,217 27 1.00    649 12 1.00   
  20-24 years 7,158 152 0.91 0.55-1.50   4,296 93 0.91 0.52-1.61   2,862 59 0.87 0.32-2.34  
  25-29 years 3,994 85 0.62 0.36-1.06 0.08 2,492 53 0.57 0.31-1.06 0.08 1,502 32 0.63 0.22-1.80  
  ≥30 years 1,315 45 0.67 0.36-1.23   825 29 0.64 0.32-1.31   490 16 0.65 0.20-2.13  
  Nulliparous 25,333 58 0.41 0.20-0.85 0.02 16,215 38 0.43 0.19-0.97 0.04 9,118 20 0.35 0.09-1.40  
Breast-feedingc
  Never 5,962 131 1.00    3,644 87 1.00    2,318 44 1.00   
  Ever 7,875 182 1.02 0.76-1.36   4,840 111 0.93 0.66-1.30   3,035 71 1.45 0.84-2.51  
  Nulliparous 25,333 58 0.61 0.37-1.02 0.06 16,215 38 0.62 0.33-1.14   9,118 20 0.53 0.21-1.30  
  1. a Not including missing data. b Adjusted for menopausal status (yes, no), oral contraceptives (never, ever), and gene mutated (BRCA1, BRCA2). c Adjusted for parity (0, 1, 2, ≥3), menopausal status (yes, no), oral contraceptives (never, ever), and gene mutated (BRCA1, BRCA2). HR hazard ratio; CI confidence interval, No., number.