Relation of time since last birth and parity to survival of young women with breast cancer.

We investigated whether survival was related to recent childbirth or parity in a cohort of 540 women diagnosed with breast cancer before the age of 45 years who were followed for up to 14 years. Women who had given birth within 2 years before their diagnosis of breast cancer were at increased risk of dying, compared with nulliparous women, with an adjusted relative risk of 3.1 (95% confidence interval = 1.8-5.4). There was a moderate association of parity with mortality, with an adjusted relative risk of 1.8 (95% confidence interval = 1.2-2.9) for women with three or more births, compared with nulliparous women.