Ask the Expert: What are the breast cancer risks for older mums?
Q: I'm in my 40s and had my first child when I was 36. Is my breast cancer risk lower because I've had children, or higher because I'm an older mum?
A: Dr Minouk Schoemaker, staff scientist at The Institute of Cancer Research London, who co-authored a recent study on breast cancer risk after childbirth, says: "There are many factors that contribute to your risk of developing breast cancer, including older age and genetic, hormonal and lifestyle factors.
"Pregnancy is known to reduce women's long-term risk of breast cancer: Your chances of developing the disease at the ages at which most cases occur, would on average be lower than that of women who haven't had children. On the other hand, studies have suggested that in the short term, pregnancy temporarily increases breast cancer risk. Our recent study looked at this dual effect in more detail, and at other factors related to childbirth, which may affect your risk.
"We found that shortly after childbirth, your risk of developing breast cancer is higher than that in women who haven't had children, all other factors being equal. Your risk increase peaks around five years after giving birth, and then gradually declines. The period of risk increase could last up to 24 years – although the length of this period looks to depend on the age when you had your first child, and how many children you've had.
"At the moment – in your 40s, with your oldest child being around 10 years old – you're still at a somewhat higher risk of developing breast cancer than other women your age who haven't had children. By the time you get to 60, your risk would be lower than that of women who haven't had children, and your pregnancy would actually have had a protective effect.
"But there's more to the story: In the long term, having children at a younger age, having more children and breastfeeding are known to lower your breast cancer risk. As an older mum, your breast cancer risk is raised compared with that of women who had their first child at younger ages. Your risk increases after pregnancy will eventually level off to the point where it would be lower than that of women who haven't had children – although this will take longer than in younger mums.
"To sum up, your risk of breast cancer changes over time, being greater at first, but eventually dipping below that of women who haven't had children. While being an older mum has raised your risk compared with younger mums, having had children will lower your overall breast cancer risk in the long run."