Skip to main content

Table 1 Selected characteristics of the participants and their mothers

From: Pre-natal exposures and breast tissue composition: findings from a British pre-birth cohort of young women and a systematic review

  n Mean % SD Median IQR
Participant characteristics at MRI examination
 Age, months 491 257.9 11.0 259.0 14.0
 BMI, kg/m2 487 23.9 4.4 23.0 5.1
 Menstrual cyclea      
  Luteal phase 70 14.4    
  Irregular periods 50 10.3    
  Follicular phase 28 5.8    
  Use of hormonal contraception 339 69.6    
 Left-right average breast volume, cm3 490 647.2 461.1 507.8 469.2
 Left-right average breast fat volume, cm3 490 406.3 349.5 292.2 327.9
 Left-right average breast water volume, cm3 490 240.9 131.2 209.8 172.4
 Left-right average breast percent water,b % 491 41.8 10.3 41.7 16.0
Maternal characteristics at participant’s birth
 Mother’s age at menarche, years 449 12.9 1.5 13.0 2.0
 Mother ever used oral contraceptive pill, % 452 96.7    
 Age when mother first used contraceptive pill, years 435 18.8 3.1 18.0 3.0
 Mother’s height, cm 446 16.6 6.5 165.1 7.6
 Mother’s age at first birth, years 463 26.5 4.7 27.0 7.0
 Mother’s age at participant’s birth, years 467 29.9 4.5 30.0 6.0
 Mother’s parity at participant’s birth      
  0 223 48.5    
  1 161 35.0    
  2+ 76 16.5    
 Mother’s pre-pregnancy BMI, kg/m2 430 22.3 3.0 21.7 3.5
 Maternal history of BC when participant was 8 years old, % 355 11.6    
Maternal characteristics at mammography
 Age, years 176 52.7 3.9 52.0 5.0
 BMI,c kg/m2 165 24.3 4.7 23.3 5.4
 Left-right average breast area, cm2 176 295.0 141.3 266.8 167.1
 Left-right average dense area, cm2 176 63.9 37.3 59.3 37.6
 Left-right average percent density, % 176 25.3 13.4 24.8 20.4
 In utero exposures      
  Placental weight, g 121 587.1 132.9 580.0 160.0
  Absolute GWG, week 0 to delivery, kg 422 12.1 3.9 12.0 5.0
  Mother drank alcohol during pregnancy, % 459 74.1    
  Mother smoked during pregnancy, % 464 10.6    
Participant characteristics at birth
 Birthweight, g 460 3395.0 472.6 3400.0 565.0
 Birth length, cm 362 50.5 2.3 50.8 2.7
 Head circumference, cm 370 34.6 1.2 34.6 1.5
 PI,d g/cm3 358 26.4 4.1 26.1 3.2
 Gestational age,e weeks      
   < 39 93 19.9    
  39 101 21.6    
  40 132 28.3    
   ≥ 41 141 30.2    
  1. Abbreviations: MRI Magnetic resonance imaging, BC Breast cancer, BMI Body mass index, GWG Gestational weight gain, PI Ponderal Index
  2. aEstimated for women not using hormonal contraception by calculating the number of days since the last menstrual period (date of MRI to start of last menstrual period). Luteal (days 14–17 to 28–31) and follicular (days 0 to 14–17) phases and an ‘irregular period’ (32+ days) were defined using average length of menstrual cycle
  3. bSections of the breast were missing in the MRI images for one participant; thus, volumetric measurements could not be ascertained, and percent water only was used
  4. cClinically measured or self-reported BMI. Median time interval between BMI assessment and mammography was 3 years (IQR 1.5 years)
  5. dPI defined as birthweight (g)/birth length (cm3)
  6. eData available only as a categorical variable