Being a mother can affect your risk of developing breast cancer.

Pregnancy 

Being pregnant can have a complex effect on your chances of developing breast cancer.

Overall, having children means your risk of breast cancer is lowered in the long term. Your risk becomes lower the more children you have and the earlier you begin your family.

Your chance might be lowered because hormone changes that occur during pregnancy leave lasting changes to your breast cells. Having children could also be linked to lifestyle choices you might make when you’re pregnant that lead to a decrease in risk, such as reducing your alcohol intake or changing your diet.

Research also suggests that temporarily, your risk of breast cancer slightly increases after you give birth, regardless of your age. We’re not sure why this is but it might be due to hormone changes in your body after you give birth. But it’s important to remember that this is only a small increase in risk that goes away after a number of years.

Breastfeeding 

If you breastfeed your children, you can slightly lower your chances of breast cancer.

The longer you breastfeed, the more your risk is lowered – for example, breastfeeding one of your children for a year would lower your chance of getting breast cancer as much as breastfeeding two of your children for six months each.

We still don’t know exactly why this happens, but breastfeeding might alter the balance of hormones in your body so you are less exposed to hormones that increase your risk of breast cancer. It could also change the cells in your breast by making them less prone to changes that could lead to cancer.

There are lots of other benefits of breastfeeding for both you and your child. Breastfeeding can lower your baby’s risk of infections, childhood leukaemia, type 2 diabetes and obesity. As well as breast cancer, breastfeeding can also lower your risk of ovarian cancer, osteoporosis (weak bones), cardiovascular disease and obesity.

But it’s important that you make the right decision for you. Whether or not you choose to breastfeed is a personal decision. Some women choose not to, and others find it difficult or are unable to for a number of reasons.

Make sure you’re still aware of any unusual changes to your breasts when you’re breastfeeding. It’s normal to find lumps in your breasts at this time as this is sometimes caused by a milk gland in your breast becoming blocked. But if you notice any unusual changes, make sure you get them checked out by your doctor. Find out more about the signs and symptoms of breast cancer.

In vitro fertilisation (IVF)

There’s no evidence that having in vitro fertilisation (IVF) treatment affects your risk of breast cancer.

Evidence so far suggests women who have received IVF treatment are no more likely to develop breast cancer than women who have not had IVF. However, IVF is a relatively new procedure and more research is needed to be sure of all the long-term health effects.

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Information last reviewed: November 2018

Next review: November 2021

Breast Cancer Now's health information is covered by NHS England's Information Standard quality mark. Find out how this resource was developed.