For women ≤40 years old, later age at first full-term pregnancy (FFTP) decreased the BC risk in BRCA1 mutation carriers (HR=0.33, 95% CI=0.12–0.90 for 24–29 years old at FFTP; HR=0.14, 95% CI=0.03–0.66 for ≥30 years old at FFTP, compared with women aged ≤23 years at FFTP; p-trend <0.001). This evidence concerns the gene BRCA1 and breast cancer.