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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