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Table 1 Baseline characteristics and in-utero exposures by case status (N = 3431)

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

Characteristics mean ± SD Controls (n = 1672) Cases (n = 1759)
Age at the time of case’s diagnosis 46.3 ± 6.0 45.0 ± 3.9
Body mass index 23.8 ± 4.4 23.8 ± 4.2
Characteristics, n (%) n (%) n (%)
Age at the time of case’s diagnosis
  < 40 272 (16.3) 211 (12.0)
  40–44 406 (24.3) 491 (27.9)
  ≥ 45 994 (59.5) 1057 (60.1)
Race
  Non-Hispanic white 1489 (89.1) 1520 (86.4)
  Non-Hispanic black 73 (4.4) 107 (6.1)
  Hispanic 66 (3.9) 79 (4.5)
  Other 43 (2.6) 53 (3.0)
Education
  High school or less 206 (12.3) 214 (12.2)
  Some college but no degree 273 (16.3) 263 (15.0)
  Associate or technical degree 260 (15.6) 249 (14.1)
  Bachelor degree 530 (31.7) 589 (33.5)
  Master or doctoral degree 403 (24.1) 444 (25.2)
BMI
  < 24.9 1216 (72.9) 1257 (71.7)
  25–29.9 306 (18.4) 362 (20.7)
  ≥ 30 146 (8.8) 134 (7.6)
Birth order
  First (oldest) 956 (57.2) 829 (47.1)
  Second 580 (34.7) 871 (49.5)
  Third or younger 136 (8.1) 59 (3.4)
Mother’s smoking history while pregnant with participant
  No 1117 (69.5) 1024 (69.2)
  Yes 491 (30.5) 455 (30.8)
Mother’s gestational diabetes
  No 1561 (99.1) 1428 (99.2)
  Yes 14 (0.9) 11 (0.8)
Mother’s preeclampsia/ eclampsia or toxemia
  No 1507 (98.2) 1359 (97.7)
  Yes 27 (1.8) 32 (2.3)
Mother’s any hypertensive disorder
  No 1506 (96.2) 1368 (95.7)
  Yes 60 (3.8) 62 (4.3)
Mother’s pregnancy-induced hypertension
  No 1445 (97.0) 1282 (96.7)
  Yes 44 (3.0) 44 (3.3)
Was this participant breastfed?
  No 948 (59.6) 948 (64.3)
  Yes 642 (40.4) 527 (35.7)
Participant’s soy formula feeding history
  No 1415 (95.8) 1221 (95.5)
  Yes 62 (4.2) 58 (4.5)
 Participant’s in-utero DES exposure
  No 1432 (96.8) 1252 (97.1)
  Yes 48 (3.2) 38 (2.9)
 Low birth weight
  Birth weight > 5.5 pounds 1475 (93.3) 1368 (91.6)
  Birth weight ≤ 5.5 pounds 106 (6.7) 125 (8.4)
High birth weight
  Birth weight < 8.8 pounds 1257 (92.7) 1114 (90.6)
  Birth weight ≥ 8.8 pounds 99 (7.3) 115 (9.4)
Short gestational length at birth
  Born ≥ 38 weeks 988 (88.5) 769 (84.8)
  Born < 38 weeks 128 (11.5) 138 (15.2)
  1. Following variables had missing data: BMI (5 controls and 1 cases), race (1 controls and 0 cases), maternal smoking during the participant’s gestation (64 controls, 280 cases), maternal gestational diabetes during the participant’s gestation (97 controls and 320 cases), maternal history of preeclampsia/eclampsia or toxemia during the participant’s gestation (138 controls and 368 cases), maternal hypertensive disorder during the participant’s gestation (106 controls and 329 cases), maternal pregnancy-related hypertension during the participant’s gestation (controls 183 and cases 433), whether the participant was breastfed (controls 82 and cases 284), participant’s soy formula feeding history (controls 195 and cases 480), mother’s DES exposure during the participant’s gestation (controls 192 cases 469), low birth weight (controls 91 and cases 266), high birth weight (controls 316 and cases 530), and short gestational age at birth (controls 603 and cases 893)