Hormonal factors

The female hormones oestrogen and progesterone can affect your breast cancer risk. Factors that can increase your risk include:

  • Taking hormone replacement therapy (HRT) – particularly if you are taking combined HRT (oestrogen and progesterone). When you stop HRT, your risk reduces again.
  • Not having children.
  • Having children after the age of 30.
  • Not breastfeeding your children, or breastfeeding for less than a year in total.
  • Starting your periods early (under the age of 12) or having a late menopause (after the age of 50).
  • Taking the contraceptive pill, although the risk reduces if you stop taking it.

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Genetic factors

There are sometimes genetic links between cancers in the same family.