Table 5

Table 5 Studies assessing the association of premature birth and the risk of breast cancer

Type of study

Author

Year

Design

Cases

Controls (or cohort)

Country/place of study

Gestational age (weeks)

OR (95% CI)

Comments


Case-control studies

[42]a

1988

PCC

153

461

USA

25–32

1.16 (0.50–1.54)

Matched analysis

33–40

Referent

[13]b

1996

NCC

571

1,525

USA

Categorical

Adjusted for age

40

Referent

38–39

0.76 (0.44–1.32)

36–37

0.96 (0.59–1.56)

Binomial

≥ 37

Referent

≤ 36

0.82 (0.37–1.82)

[14]

1996

PCC

1123

1371

USA

Nonpreterm

Referent

Adjusted for age, menopausal status, and maternal smoking

Preterm

1.1 (0.5–2.1)

[32]a

1997

NCC

1,010

2,625

Sweden

≥ 33

Referent

Adjusted for maternal age, matermal socioeconomic status, maternal parity, maternal pre-eclampsia or eclampsia, neonatal jaundice, severe prematurity, twin, and birth weight

≤ 32

3.96 (1.46–10.81)

[33]b

1998

PCC

502

433

USA

≥ 43

1.5 (0.8–2.6)

Crude ORs

37–42

Referent

≤ 36

0.9 (0.5–1.8)

[15]a,b

2000

LCC

480

2,854

USA

≥ 37

Referent

Crude ORs

33–36

1.34 (0.85–2.13)

≤ 32

0.55 (0.19–1.57)

[34]a,b

2001

LCC

87

87

Sweden

≥ 40

8.4 (1.3–54.4)

Matched analysis by conditional logistic regression

37–40

3.4 (0.7–17.0)

33–36

3.5 (0.7–17.5)

≤ 32

Referent

[25]a

2003

LCohort

127

(1,483)

Sweden

≥ 33

1.08 (0.64–1.70)

Standardized incidence ratio (expected/observed)

≤ 32

0.92 (0.57–1.41)

[45]a,b

2004

LCC

2,471

9,801

USA

≥ 37

Referent

Adjusted for age and maternal age at first birth

32–36

0.91 (0.72–1.13)

≤ 31

1.43 (0.90–2.28)

[20]b

2005

PCC

1,424

1,457

Poland

≥ 37

Referent

Adjusted for age, education, age at menarche, menopausal status and age at menopause, age at first full-term pregnancy, number of full-term pregnancies, family history of breast cancer among first-degree relatives, mammography screening, and current body mass index

≤ 36

1.01 (0.75–1.32)

Cohort studies

[62]c

2000

LCohort

12

273

Sweden

35

0.2 (0.01–1.3)

Standardized incidence ratio

33–34

0.7 (0.1–2.0)

31–32

2.3 (0.7–5.3)

<31

6.7 (1.4–19.5)

[16]c

2001

LTCCS

2,265

9,060

Sweden

33–36

Referent

Crude ORs

37–38

1.8 (0.83–4.0)

40–44

2.0 (0.88–4.6)

[29]c

2005

LCohort

367

5,346

Sweden

1 week increase

<50 years

0.94 (0.83–1.07)

[40]c

2006

Cohort

97

5,847

USA

<39

0.77 (0.42–1.4)

Adjusted for age

39

1.38 (0.78–2.4)

40

Referent

41+

1.33 (0.67–2.6)

[31]b

2006

Cohort

249

1024

USA

≥ 43

0.7 (0.2–2.7)

Adjusted for: age at diagnosis, diagnosis year, stage at diagnosis, and birth order, with exception of birth order, which is adjusted for maternal age

37–42

Referent

<37

1.4 (0.7–2.9)

P for trend = 0.3


Cohort, cohort study; LCC, case-control study with linkage with population and cancer registry data; LTCCS, twin case-control study by using linkage with birth and cancer registry data; NCC, nested case-control study in cohort; PCC, population-based case-control study. aWe included this study in the meta-analysis with categories of ≥33 versus ≤32 months (reference). bWe included this study in the meta-analysis with categories of ≥37 versus ≤36 months (reference). cWe did not include these studies in the meta-analysis because they employed different categories or a continuous scale, or they did not provide the numbers of cases and controls in the report.

Park et al. Breast Cancer Research 2008 10:R8   doi:10.1186/bcr1850

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