Pregnancy and Breast Cancer Risk

The decision to have children is very personal – some people want children and some do not. Some have their children when they are young whilst others are delaying getting pregnant until they are a bit older. Some have only one or two children whilst others have many more and some women have difficulty in falling pregnant.  In the Victorian era it would have been common to start having a family in the late teens. However today many women work, build careers or travel and are having their babies in their late 30’s. Partners can share in this decision making.

There is a complex relationship between pregnancy and breast cancer risk and many of these factors have an effect.

So what are some things we know about pregnancy and breast cancer risk? 

Whilst a woman is pregnant she will not have periods and this will reduce the number of menstrual cycles that she has over her lifetime and that may reduce the risk of breast cancer. But it is not as simple as that as research has shown that there is a small risk of breast cancer for up to 10 years after having a baby. However, after this initial increase in risk, there is a long-term lower risk of breast cancer.

Age of first pregnancy: Women who have a first pregnancy under the age of 30 will have a lower risk (20-35%) of developing breast cancer in the long term compared with those who never have children.

Women who have a first baby after the age of 30 will have a higher risk of breast cancer than younger women and over the age of 35 there is a 30% increase in risk.

Number of Pregnancies: Women who have never had a full-term pregnancy will have a higher risk of breast cancer. Pregnancies do have a protective role in breast cancer risk after the first 10-20 years. The more babies you have, the lower the risk. There is a reduction in one’s individual risk of breast cancer by a quarter for each birth a woman has and having over 5 babies can significantly reduce her individual risk of breast cancer by half.