Pregnancy and Breast Cancer

Interesting Facts:

Very few pregnant women are diagnosed with breast cancer. But more women are choosing to have children later in life. Because the risk of breast cancer increases as women get older, doctors expect there will be more cases of breast cancer during pregnancy in the future.

Estimates are that about 1 out of 1,000 pregnant women is diagnosed with cancer, with about 3,500 cases diagnosed each year. The most common type of cancer found during pregnancy or in the first year after pregnancy is breast cancer. You may hear this called gestational breast cancer or pregnancy-associated breast cancer.

Breast cancer risk

What is cancer?

Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person’s life, normal cells divide more quickly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.

Cancer cells keep on growing and dividing, which makes them very different from normal cells. Instead of dying, they outlive normal cells and keep making new, abnormal cells. Hormones like estrogen help normal breast cells grow and divide, but hormones can also promote the growth of breast cancer cells.

How your menstrual cycles affect breast cancer risk

Women who are exposed to higher levels of estrogen over longer periods of time seem to have a slightly higher risk for breast cancer. This includes women who had more menstrual periods, such as those who started menstruating before age 12 or who went through menopause after age 55.

How pregnancy affects breast cancer risk later in life

Pregnancy causes many hormone changes in the body. For one thing, pregnancy stops the monthly menstrual cycles and shifts the hormone balance toward progesterone rather than estrogen. This is why women who become pregnant while they are young and have many pregnancies may have a slightly lower risk of breast cancer later on. Women who have had no children or who had their first pregnancy after age 30 have a slightly higher breast cancer risk later in life.