Table 1.

Risk factors of PABC

Risk factors	Significance	Reference
Family history of breast cancer	Increased risk of PABC ≤ 2 years postpartum (HR 3.28, P = 0.001)	[12]
Genetic predisposition	BRCA1/2 carriers in PABC (25 vs. 11.5%, P = 0.034)	[12, 58]
Age at first pregnancy > 30 years old	5.3% increased risk of PABC per each year postponing pregnancy after 25 years of age	[59]
	No long-term BC protection from 1st pregnancy after age 35 years	[60]
Early age at menarche	Increased risk of PABC with early age at menarche (< 13 vs. ≥ 13 years) (HR 2.165, P < 0.001)	[4]
Little-to-no breastfeeding	4.3% decreased lifetime risk of BC by each 12 months of breastfeeding (P < 0.0001)	[61]
	Decreased risk of BC with breastfeeding > 12 months (HR 0.74, P < 0.001)	[62]
Overweight	Overweight women are at higher risk of PABC (HR 1.427, P = 0.011)	[4]