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
| Â | 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%)* | Â | n = 313 (87%)* | Â | n = 860 (86%)* | Â |
   < 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%) | Â | n = 355 (98%) | Â | n = 991 (99%) | Â |
   Yes | 89.9 |  | 88.2 |  | 93.0 |  |
   No | 10.0 |  | 11.8 |  | 7.0 |  |
Parous women | Â | Â | Â | Â | Â | Â |
Age at first birth | n = 85 (96%) | Â | n = 300 (96%) | Â | n = 880 (95%) | Â |
   < 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%) | Â | n = 313 (100%) | Â | n = 922 (100%) | Â |
   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%) | Â | n = 209 (67%) | Â | n = 640 (69%) | Â |
   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 |  |