Table 2 The population attributable risks and estimated number of new cancer cases in Korean women caused by modifiable reproductive factors in the year 2010

Breast

Pregnancy/age at first birth

8.0 (7.4-8.6)

1152 (1066–1246)

(Nullipara or age at first birth ≥ 24 years)

Total period of breast feeding^a

3.1 (3.1-3.2)

453 (441–464)

(Duration of breast feeding ≤ 6 months)

Oral contraceptive use (Ever)

5.3 (5.1-5.5)

763 (732–795)

Hormone replacement therapy use (Ever)^b

0.3 (0.2-0.3)

37 (29–44)

Total

16.7 (15.8-17.6)

2404 (2283–2535)

Ovary

Pregnancy (Nulliparous)

1.2 (1.2-1.2)

24 (24–24)

Breast feeding experience (Never)^a

2.9 (2.8-2.9)

55 (55–56)

Tubal ligation (No)^a

24.5 (23.0-26.2)

473 (444–504)

Oral contraceptive use (Never)

53.3 (27.9-100.0^d)

1027 (537–1927)

Total

81.9 (55.0-100.0 ^d)

1579 (1059–1927)

Attributed % of cases

% of breast cancer in women

16.7 (15.8-17.6)

% of ovary cancer in women

81.9 (55.0-100.0^d)