Table 2 Odds Ratios of breast cancer risk in terms of A) pregnancy and breastfeeding (either status or duration) and B) breastfeeding and number of children before and after adjusting for the effect of each other and all other risk factors in multivariable logistic models

A. Pregnancy

   No

1.00

   Yes

0.69 (0.49,0.97)

0.03

0.89 (0.62,1.28)

0.54

1.07 (0.66,1.72)

0.79

   Breastfeeding ¹

   No

1.00

   Yes

0.69 (0.57,0.82)

<0.001

0.63 (0.45,0.89)

<0.01

0.72 (0.59,0.90)

<0.01

   Breastfeeding by duration ^{1, 2}

   Never

1.00

   ≤6 months

0.71 (0.58,0.88)

0.65 (0.45,0.94)

0.73 (0.57,0.93)

   7-12 months

0.76 (0.58,0.98)

0.69 (0.47, 1.03)

0.86 (0.64,1.16)

   >1 year

0.61 (0.48,0.77)

<0.001³

0.56 (0.38,0.81)

<0.001³

0.68 (0.51,0.91)

0.04³

B. Breastfeeding

   No

1.00

   Yes

0.69 (0.57,0.83)

0.03

0.72 (0.58,0.88)

<0.01

0.72 (0.58,0.90)

<0.01

   Number of children

   None

1.00

   One

0.90 (0.59,1.37)

1.06 (0.69,1.64)

1.29 (0.76,2.18)

   Two

0.84 (0.61,1.15)

1.04 (0.74,1.48)

1.27 (0.76,2.18)

   Three

0.68 (0.49,0.94)

<0.01³

0.90 (0.62,1.29)

0.25³

1.14 (0.82,1.99)

0.87