Study Suggests Why Giving Birth in 20s Reduces Breast Cancer Risk

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Researchers know that women who haven’t had a full-term pregnancy or have their first child after age 30 have a higher risk of breast cancer than women who give birth before age 30.

When breast cells are made during adolescence, they are immature and very active until your first full-term pregnancy. Immature breast cells respond to the hormone estrogen as well as hormone-disrupting chemicals, such as bisphenol A (BPA) and parabens, in plastic and other products. Breast cancer is uncontrolled growth of breast cells. Your first full-term pregnancy makes the breast cells fully mature and grow in a more regular way.

Still, researchers haven’t been sure how the protective process of early pregnancy happened at the cellular level. In other words, they didn’t know the mechanics of exactly which breast cells were involved and how they provided protection against breast cancer.

A new study suggests how and why women who give birth in their 20s have a lower risk of breast cancer.

The research was published in the July 2013 issue of the journal Cell Stem Cell.

Read the abstract of “Molecular Profiling of Human Mammary Gland Links Breast Cancer Risk to a p27 Cell Population with Progenitor Characteristics.”

In the study, researchers looked at the activity of specific cells in breast tissue samples from thousands of women collected over a period of 20 years.

The researchers found that a woman who had a full-term pregnancy in her 20s had a lower number of certain breast cells called mammary gland progenitors. These cells have the ability to divide and become milk-producing cells. A full-term pregnancy before age 30 also reduced the ability of mammary gland progenitor cells to grow and divide. If the cells can’t grow and divide, it’s less likely they’ll develop a mutation that leads to breast cancer.

By comparing many samples of breast cancer tissue, the researchers found that women at high risk for breast cancer, such as women with an abnormal BRCA1 or BRCA2 gene, have higher-than-average numbers of mammary gland progenitor cells.

Overall, women who had a full-term pregnancy in their 20s had the lowest number of mammary gland progenitor cells, even when compared to women who had never been diagnosed with breast cancer and had never been pregnant. Still, women who gave birth before age 30 and later developed breast cancer had a higher-than-average number of mammary gland progenitor cells.

So the researchers think that determining how many mammary gland progenitor cells each woman has may help doctors figure out which women are at high risk for breast cancer.

While the results of this research are very exciting, much more research is necessary before we can say for sure that knowing the number of mammary gland progenitor cells a woman has allows her risk for breast cancer to be calculated.

The decision to have a child is very personal, complicated, and requires commitment and support. The inability to have children can be very painful and the prospect of having a child without a partner may be daunting for some women.

Some women may choose not to have children. Others may choose to wait until they are older to have children. Many women who would like to get pregnant are stopped by infertility. After a breast cancer diagnosis, the opportunity to have children can be hindered by lingering treatment side effects (including infertility), and taking hormonal therapy medicine to reduce the risk of the cancer coming back (it's unsafe to take hormonal therapy while you're pregnant). In addition, research has not been done specifically to find out how pregnancy hormones affect risk of recurrence for women who've had hormone-receptor positive breast cancer. If you fit into this category and want to get pregnant, talk to your doctor and weigh any risks.

If having children earlier rather than later is an option for you, you may want to do that. Still, this is a highly individual decision affected by many factors besides breast cancer risk.

Whether or not you have children at a younger age, there are lifestyle choices you can make to keep your breast cancer risk as low as it can be:

  • eating a healthy diet that’s low in processed foods and sugar
  • avoiding alcohol
  • maintaining a healthy weight
  • exercising daily
  • not smoking

These are just a few of the steps you can take. Visit the Breastcancer.org Lower Your Risk section for more options.

And stayed tuned to Breastcancer.org Research News for the latest information on studies on mammary gland progenitor cells.

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