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 |  |