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Table 3 Association of breast cancer grade by reproductive and family history variables

From: Effect of reproductive factors on stage, grade and hormone receptor status in early-onset breast cancer

Reproductive and hormonal Grade 1–2 Grade 3–4 OR (for grade 95% CI P
Age at menarche (years)
   <12 15 (18.8) 33 (25.4) 1.0 (ref)   
   ≥ 12 65 (81.2) 97 (74.6) 0.7 0.4–1.5 0.38
Age at first full-term pregnancy (years)
   No full-term pregnancies 27 (33.3) 35 (26.5) 1.0 (ref)   
   <20 5 (6.2) 23 (17.4) 3.2 1.0–9.9 0.05
   20–24 25 (30.9) 34 (25.8) 1.0 0.4–2.1 0.95
   25–29 17 (21.0) 26 (19.7) 1.4 0.6–3.1 0.43
   30–34 7 (8.6) 14 (10.6) 2.5 0.8–7.5 0.10
   Trend      0.27
Total live births
   0 27 (33.3) 35 (26.5) 1.0 (ref)   
   1–2 45 (55.6) 78 (58.3) 1.5 0.8–2.8 0.25
   3 or more 9 (11.1) 19 (15.2) 1.7 0.6–4.6 0.30
   Trend      0.22
Total miscarriages (gravid women)
   0 50 (82.0) 73 (70.2) 1.0 (ref)   
   1 or more 11 (18.0) 31 (29.8) 2.0 0.9–4.5 0.08
Total induced abortions (gravid women)
   0 40 (65.6) 68 (65.4) 1.0 (ref)   
   1 or more 21 (34.4) 36 (34.6) 1.0 0.5–1.9 0.92
Breastfeeding (parous women)
   Never 15 (27.8) 34 (35.0) 1.0 (ref)   
   Ever 39 (72.2) 63 (65.0) 0.8 0.4–1.6 0.51
Months between last full-term pregnancy and diagnosis
   No full-term pregnancy 27 (33.3) 35 (26.5) 1.0 (ref)   
   0–23 19 (23.4) 27 (20.4) 1.2 0.5–2.6 0.71
   ≥ 24 35 (43.2) 70 (53.0) 1.7 0.9–3.5 0.12
   Trend      0.12
Oral contraceptive use
   Never 10 (12.4) 21 (15.9) 1.0 (ref)   
   Ever 71 (87.6) 111 (84.1) 0.7 0.3–1.6 0.42
Total months of oral contraceptive useb
   None 10 (13.2) 21 (16.0) 1.0 (ref)   
   1–35 24 (31.6) 32 (24.4) 0.8 0.4–2.0 0.68
   36–83 17 (22.4) 38 (29.0) 1.5 0.6–3.7 0.35
   84 or more 25 (32.9) 40 (30.5) 1.2 0.5–2.8 0.64
   Trend      0.78
Family history of breast or ovarian cancerc
   No family history 65 (80.2) 113 (86.9) 1.0 (ref)   
   Mother or sister 16 (19.8) 17 (13.1) 0.7 0.3–1.4 0.29
  1. aAnalyses adjusted for age at diagnosis and education (higher of self or spouse). bFive records missing total months of oral contraceptive use. cTwo records were excluded because proband reported being adopted. CI, confidence interval; OR, odds ratio.