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Table 4 Case-only odds ratios for estrogen receptor-negative breast cancer in relation to participant’s exposures

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

Characteristics ER+ (n = 1356) ER− (n = 338) OR (95% CI OR (95% CI)
Preeclampsia/eclampsia/toxemia n (%) n (%)   
 No 1078 (98.2) 237 (95.9) 1.00 1.00
 Yes 20 (1.8) 10 (4.1) 2.27 (1.05–4.92) 2.23 (0.94–5.30)*
Gestational hypertension§
 No 1031 (97.7) 222 (97.4) 1.00 1.00
 Yes 24 (2.3) 6 (2.6) 1.16 (0.47–2.87) 1.08 (0.40–2.88)*
Any hypertensive disorder
 No 1084 (96.1) 237 (93.7) 1.00 1.00
 Yes 44 (3.9) 16 (6.3) 1.66 (0.92–3.00) 1.56 (0.82–2.98)*
Maternal smoking
 No 812 (69.6) 175 (67.8) 1.00  
 Yes 355 (30.4) 83 (32.2) 1.08 (0.81–1.45)  
Low birth weight
 Birth weight > 5.5 pounds 1075 (91.6) 247 (92.2) 1.00 1.00
 Birth weight ≤ 5.5 pounds 98 (8.4) 21 (7.8) 0.93 (0.57–1.52) 0.86 (0.49–1.49)#
High birth weight
 Birth weight < 8.8 pounds 873 (90.3) 205 (92.8) 1.00 1.00
 Birth weight ≥ 8.8 pounds 94 (9.7) 16 (7.2) 0.72 (0.42–1.26) 0.64 (0.35–1.17)#
Breastfed
 No 737 (63.2) 172 (67.2) 1.00  
 Yes 428 (36.8) 84 (32.8) 0.84 (0.63–1.12)  
Soy-fed (formula made from soy)
 No 958 (95.3) 218 (96.0) 1.00  
 Yes 47 (4.7) 9 (4.0) 0.84 (0.41–1.74)  
DES exposure during pregnancy
 No 994 (97.0) 211 (97.2) 1.00  
 Yes 31 (3.0) 6 (2.8) 0.91 (0.38–2.21)  
Short gestational length at birth
 Born ≥ 38 weeks 617 (85.3) 131 (84.0) 1.00 1.00
 Born < 38 weeks 106 (14.6) 25 (16.0) 1.11 (0.69–1.79) 0.94 (0.56–1.57)#
  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