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Table 4 Meta-analysis of the association between various birth size measurements and percent breast density, stratified by potential sources of between-study heterogeneity

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

Perinatal factor

Number of studiesa

Average relative changeb (95 % CI)

z-score p value

I 2 statistic (%)

References

Birth size measurements:

 Birthweight

  Overallc

9

1.59 (1.58–1.59)

<0.001

100.0

[21, 22, 25, 26, 33, 35, 49, 50]; present study

  Using Andersen et al. [35] OR2d

9

1.59 (1.58–1.59)

<0.001

100.0

  Excluding present study

8

1.63 (1.62–1.63)

<0.001

100.0

 Menopausal status

  Pre-menopausal women

3

1.03 (1.02–1.04)

<0.001

38.1

[21, 22]; present study

  Post-menopausal women

3

1.72 (1.71–1.72)

<0.001

99.7

[21, 22, 26]

 Source of birthweight data

  Self-/parent report

4

0.99 (0.99–1.00)

0.117

91.0

[21, 22, 35, 50]

  Hospital records

5

1.67 (1.66–1.67)

<0.001

10.0

[25, 26, 33, 49] present study

 Breast density assessment method

  Radiographer-assessed

4

1.05 (1.00–1.10)

0.066

49.7

[25, 33, 35, 49]

  Computer-assisted

5

1.59 (1.58–1.59)

<0.001

100.0

[21, 22, 26, 50] present study

 Restricted to hospital records

  Radiographer-assessed

3

1.07 (1.02–1.13)

0.013

33.3

[25, 33, 49]

  Computer-assisted

2

1.67 (1.66–1.67)

<0.001

100.0

[26]; present study

 Quality scoree

  Highest tertile (≥50)

3

1.67 (1.66–1.67)

<0.001

100.0

[26, 35]; present study

  Middle tertile (40–50)

3

0.99 (0.99–1.00)

0.142

94.7

[22, 48, 50]

  Lowest tertile (<40)

3

1.04 (0.99–1.09)

0.160

26.3

[21, 25, 35]

 Birth length

  Overall

3

1.02 (1.00–1.04)

0.051

89.2

[25, 26]; present study

 Head circumference

  Overall

2

1.11 (1.11–1.11)

<0.001

100.0

[26]; present study

 Maternal age

  Overall

5

1.01 (1.01–1.02)

<0.001

31.7

[20, 22, 25, 50]; present study

  Excluding present study

4

1.01 (1.01–1.02)

<0.001

21.9

 

  Menopausal status

   Pre-menopausal women

3

1.00 (0.99–1.02)

0.539

0.0

[20, 22]; present study

   Post-menopausal women

3

1.01 (1.01–1.02)

<0.001

0.0

[20, 22, 50]

  Quality score (maximum 59)d

   Highest (≥40)

3

1.01 (1.01–1.02)

<0.001

17.4

[22, 50]; present study

   Lowest (<40)

2

1.00 (0.97–1.04)

0.898

67.2

[20, 25]

  1. aLope et al. [20] was not included in the birthweight meta-analysis, owing to concerns about the validity of a summary trend measure across the limited number of categories (three groups)
  2. bDue to the high between-study heterogeneity in most strata, these average estimates should be interpreted simply as indicators of the direction of the trend in breast density with increasing birth size
  3. cMeta-analysis uses OR1 from Andersen et al. [35] as reported in Table S3, which is adjusted for age at screening and birth cohort: OR 0.98; 95 % CI 0.90–1.07
  4. dMeta-analysis uses OR2 from Andersen et al. [35] as reported in Table S3, which is adjusted for age at screening, birth cohort and BMI at age 13 years: OR 1.11; 95 % CI 1.02–1.22
  5. eRange 0–59; see Methods section of main text and Additional file 1: Methods 3 for description of how study quality scores were developed
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Breast Cancer Research

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