Compared to those with an early first birth (≤20 years), women with a later age at first birth (>30 years) were at slightly increased risk of luminal A-like (OR = 1.19, 95% CI 0.99–1.43) and luminal B-like HER2-negative breast cancer (OR = 1.60, 95% CI 1.10–2.32, p-trend = 0.07 and 0.01, respectively). This evidence concerns the gene ERBB2 and breast cancer.