Birth length (per 2 cm increment) was positively associated with risk of Luminal A breast cancer (HR = 1.2, 95% CI, 1.0–1.3), Luminal B (HER2+) breast cancer (HR = 1.3, 95% CI, 1.0–1.7), and TN breast cancer (HR = 1.4, 95% CI, 1.0–1.9), but there were no clear associations with Luminal B (HER2-) and HER2 type (p for heterogeneity 0.8). Here, ERBB2 is linked to breast cancer.