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Pregnancy And Breastfeeding

There can be several stages in a woman’s reproductive life that influence her risk of developing breast cancer. These stages can increase or decrease that risk in different ways.

A woman’s life stages are related to hormonalHormone:
A natural substance released into the body by the endocrine glands, such as the thyroid, adrenal gland or ovaries.
changes that occur naturally, such as when you start and stop menstruating, if or when you become pregnant and carry the pregnancy to full term, and if you are able and choose to breastfeed.

Pregnancy And Breast Cancer Risk

There is evidence that pregnancy and childbirth influence your risk of breast cancer. Generally, the younger a woman is when she gives birth, the lower her risk of developing breast cancer.

Women who have their first child before their early 30’s have a slightly lower risk of breast cancer than women who give birth later or women who have not had a full-term pregnancy. Having more than one child also decreases your breast cancer risk and with every subsequent child your risk decreases further. This is because the hormones involved in a pregnancy carried to full-term mature the breast tissue in a way that seems to protect against breast cancer.  

There is a short-term increase in the risk of developing breast cancer after childbirth. This period of increased risk may last for up to several years following the birth of your child, and is likely a result of hormonal changes that promote cellCell:
The basic structural and functional unit of all organisms.
growth in breast tissue.

Breastfeeding Offers Protective Benefits For The Mother

If breastfeeding is an option for you and your baby, evidence suggests that it can reduce the risk of developing breast cancer. 

The biggest benefits are from longer periods of breastfeeding, for a year or more with one child or over several births. The effect of breastfeeding on breast cancer risk may be related to the fact that women usually stop menstruating while they are still breastfeeding, meaning they have fewer periods over their lifetime and therefore lower exposure to estrogenEstrogen:
A female sex hormone that is produced mainly in the ovaries. A woman’s levels of estrogen fluctuate throughout her life. Estrogen has been linked to the development of breast cancer and may promote the growth of cancer cells.
. Breast tissue is susceptible to the effects of estrogen, and estrogen exposure plays a role in the development of breast cancer. Changes in hormones that occur during breast feeding may also affect breast tissue in a way that protects against breast cancer.

Canadian Breast Cancer Foundation encourages you to learn about your breast health, breast cancer risk, ways to reduce your risk, and the benefits and limitations of screeningScreening:
The search for diseases such as breast cancer in people without symptoms. Mammography is an important tool for breast cancer screening and earlier detection.
for the earlier detection of breast cancer. To inform your decisions, we also encourage you to consider speaking to a health care provider.


Canadian Breast Cancer Foundation. (2010). Earlier Detection and Diagnosis of Breast Cancer: A Report from It’s About Time! A Consensus Conference. Toronto, ON: Canadian Breast Cancer Foundation. 

National Cancer Institute. Reproductive History and Breast Cancer Risk.  Accessed June 23, 2014.

Collaborative Group on Hormonal Factors in Breast Cancer. (2002). Breast cancer and breastfeeding.  The Lancet, 360 (9328), 187-195.