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Table 4 Association of estrogen receptor status and reproductive and family history variables

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

Reproductive and family history characteristics ER-positive or borderline tumors (n = 95) ER-negative tumors (n = 87) ORa 95% CI P
Age at menarche (years)b
   <12 16 (17.0) 19 (22.4) 1.0 (ref)   
   ≥ 12 78 (83.0) 66 (77.6) 0.7 0.3–1.5 0.42
Age at first full-term pregnancy (years)
   No full-term pregnancies 27 (28.4) 27 (31.0) 1.0 (ref)   
   <20 10 (10.5) 16 (18.4) 1.5 0.6–4.0 0.43
   20–24 26 (27.4) 19 (21.8) 0.7 0.3–1.6 0.39
   25–29 23 (24.2) 16 (18.4) 0.7 0.3–1.7 0.45
   30–34 9 (9.5) 9 (10.3) 1.2 0.4–3.6 0.80
   Trend      1.0
Total live births
   0 27 (28.4) 27 (31.0) 1.0 (ref)   
   1–2 57 (60.0) 49 (56.3) 0.9 0.4–1.7 0.68
   3 or more 11 (11.6) 11 (12.6) 1.0 0.3–2.8 0.97
   Trend      0.86
Total miscarriages (gravid women)
   0 61 (80.3) 42 (65.6) 1.0 (ref)   
   1 or more 15 (19.7) 22 (34.4) 2.1 1.0–4.6 0.05
Total induced abortions (gravid women)
   0 48 (63.2) 44 (68.8) 1.0 (ref)   
   1 or more 28 (26.8) 20 (31.2) 0.7 0.4–1.5 0.42
Breastfeeding (parous women)
   Never 12 (17.6) 29 (48.3) 1.0 (ref)   
   Ever 56 (82.4) 31 (51.7) 0.2 0.1–0.5 <0.001
Months between last full-term pregnancy and diagnosis
   No full-term pregnancy 27 (28.4) 27 (31.0) 1.0 (ref)   
   0–23 19 (20.0) 16 (18.4) 0.9 0.4–2.0 0.71
   ≥ 24 49 (51.6) 44 (50.6) 0.9 0.4–1.8 0.77
   Trend      0.78
Oral contraceptive use
   Never 19 (20.0) 12 (13.8) 1.0 (ref)   
   Ever 76 (80.0) 75 (86.2) 1.6 0.7–3.4 0.28
Total months of oral contraceptive usec
   None 19 (20.2) 12 (14.6) 1.0 (ref)   
   1–35 24 (25.5) 23 (28.0) 1.1 0.5–2.6 0.81
   36–83 16 (17.0) 20 (24.4) 1.5 0.6–3.7 0.42
   84 or more 35 (37.2) 27 (32.9) 0.9 0.4–2.1 0.85
   Trend      0.78
Family history of breast or ovarian cancerd
   No family history 75 (79.8) 71 (82.6) 1.0 (ref)   
   Mother or sister 19 (20.2) 15 (17.4) 0.9 0.4–1.9 0.72
  1. aAnalyses adjusted for age at diagnosis and education (higher of self or spouse).
  2. bThree records missing age at menarche. cSix records missing total months of oral contraceptive use. dTwo records were excluded because proband reported being adopted. CI, confidence interval; ER, estrogen receptor; OR, odds ratio.