Table 3.

Summary of meta-analysis results for case-case analyses (Reference group: Luminal A; n = 18 studies)

Reproductive factors	Contrast	Luminal B/ ER + , PR + , HER +	HER2-overexpressing/ER-, PR-, HER +	Triple Negative/ basal-like/ER-, PR-, HER-
Age at menarche (n = 13)	Later vs. earlier	NS +	NS +	NS-
Age at menopause (n = 6)	Later vs. earlier	–	NS +	NS-
Menopausal status (n = 7)	Post vs. pre/peri	NS +	S +	S +
Age at first birth (n = 12)	Nulliparous/later vs. earlier age at FB	NS-	S-	S-
Parity (n = 16)	Higher parity vs. low/nulliparity	NS +	NS +	S +
Breastfeeding (n = 10)	Ever /longer vs. never/shorter	NS-	NS-	S-
OC use (n = 9)	Ever/longer vs. never/shorter	S-	NS +	NS +
HRT (n = 5)	Ever vs. never	NS-	NS +	NS +

Abbreviations: S- Significant lower risk, S + Significant higher risk, NS + Non-significant higher risk, NS- Non-significant lower risk, FB First birth, OC Oral contraceptive, HRT Hormone replacement therapy