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Table 5 Case-only odds ratios for estrogen receptor-negative breast cancer (excluding in situ) in relation to participant’s exposures

From: Perinatal and postnatal exposures and risk of young-onset breast cancer

Characteristics ER+ (n = 1124) ER− (n = 307) OR (95% CI OR (95% CI)
Preeclampsia/eclampsia/toxemia n (%) n (%)   
 No 890 (98.0) 213 (95.9) 1.00 1.00
 Yes 18 (2.0) 9 (4.1) 2.09 (0.93–4.72) 2.04 (0.81–5.13)*
Gestational hypertension§
 No 853 (97.9) 198 (97.1) 1.00 1.00
 Yes 18 (2.1) 6 (2.9) 1.44 (0.56–3.66) 1.29 (0.47–3.53)*
Any hypertensive disorder
 No 895 (96.1) 213 (93.4) 1.00 1.00
 Yes 36 (3.9) 15 (6.6) 1.75 (0.94–3.26) 1.62 (0.81–3.20)*
Maternal smoking
 No 677 (70.2) 156 (67.2) 1.00  
 Yes 287 (29.8) 76 (32.8) 1.15 (0.85–1.56)  
Low birth weight
 Birth weight > 5.5 pounds 885 (91.3) 225 (92.2) 1.00 1.00
 Birth weight ≤ 5.5 pounds 84 (8.7) 19 (7.8) 0.89 (0.53–1.49) 0.80 (0.44–1.44)#
High birth weight
 Birth weight < 8.8 pounds 715 (89.4) 185 (92.0) 1.00 1.00
 Birth weight ≥ 8.8 pounds 85 (10.6) 16 (8.0) 0.73 (0.42–1.27) 0.66 (0.36–1.22)#
Breastfed
 No 606 (62.9) 151 (65.4) 1.00  
 Yes 358 (37.1) 80 (34.6) 0.90 (0.66–1.21)  
Soy-fed (formula made from soy)
 No 787 (95.5) 197 (96.1) 1.00  
 Yes 37 (4.5) 8 (3.9) 0.86 (0.40–1.88)  
DES exposure during pregnancy
 No 818 (96.7) 189 (97.4) 1.00  
 Yes 28 (3.3) 5 (2.6) 0.77 (0.29–2.03)  
Short gestational length at birth
 Born ≥ 38 weeks 517 (85.6) 118 (84.3) 1.00 1.00
 Born < 38 weeks 87 (14.4) 22 (15.7) 1.11 (0.67–1.84) 0.91 (0.52–1.60)#
  1. ¥Uadjusted analysis
  2. §Excluding preeclampsia/eclampsia
  3. *Adjusted for whether or not the participant was their mother’s first baby and excluding women who themselves had a preeclamptic pregnancy
  4. #Adjusted for whether the participant’s gestation was complicated by preeclampsia