Early menarche, late menopause, or late 1st pregnancy increases risk. Women who have a 1st pregnancy after age 30 are at higher risk than those who are nulliparous.

初潮早，停经晚，或首次妊娠晚，均可增加癌症危险。30岁后怀第一胎的妇女，其危险性要高于未产妇。

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Epidemiologic studies over the past 40 years have identified numerous risk factors for breast cancer, including: older age, an early age at menarche, a late age at first full-term birth, not having children, a family history of breast cancer in a first-degree relative, greater height, higher circulating estrogen levels, postmenopausal hormone use, breast density, history of breast biopsies, obesity (for postmenopausal breast cancer), and exposure to ionizing radiation.

FORBES: After 40 Years Of Research, What Do We Know About Preventing Breast Cancer?