Age at first childbirth and breast cancer survival: a prospective cohort study

Abstract

Abstract Objective Late age at first childbirth is a well-established risk factor for breast cancer. Previous studies have, however, shown conflicting results to whether late age at first childbirth also influences the prognosis of breast cancer survival. The aim of this study was to examine age at first birth in relation to survival after breast cancer diagnosis. Results We used information from the Malmö Diet and Cancer study. At baseline 17,035 women were included. All women were followed from the year they developed breast cancer until they either died or until the end of follow-up. All women were asked how many children they had given birth to and were then divided into different groups, ≤ 20, > 20 to ≤ 25, > 25 to ≤ 30 and > 30. Nulliparous women form a separate group. Survival analyses were then performed using Cox proportional hazard survival analysis. Women in all age groups had a lower risk of breast cancer specific death as compared to the reference group ≤ 20, however non-significantly. Nulliparous women had a higher risk of breast cancer specific death as compared to the same reference group, however these results were not statistically significant. We could not see any negative effect of late first childbirth on breast cancer specific survival.

Keywords

• Breast cancer risk
• Age at first childbirth
• Nulliparity
• Survival
• Reproductive factors