Most of the benefits of motherhood are intangible, emotional, and social. But here's some evidence that pregnancy gives you a gift of health -- an edge against developing breast cancer.
Pregnancy and Breastfeeding Lower Estrogen Exposure
Pregnancy before age 30 and breastfeeding reduces a woman's total number of lifetime menstrual cycles, which is thought to be one reason they help lower your risk. The hormone estrogen fuels 80% of all breast cancers. Since pregnancy and lactation reduce your estrogen levels, your risk is decreased each time you are pregnant and while you are nursing your baby.
Does My Age At Pregnancy Matter?
According to the National Cancer Institute, having a full-term pregnancy at or before age 20 offers the most protection against developing breast cancer. This may cut your risk of breast cancer in half. Breastfeeding keeps your estrogen levels low, so you don't have pre-pregnancy levels of estrogen until your baby is weaned.
Having your first pregnancy at age 30 or older offers less protection against breast cancer. Alpha-fetoprotein, a protein produced by the fetus during pregnancy, helps regulate fetal growth. It can also help suppress breast cancer cells. In women over 30, alpha-fetoprotein works differently, and may actually help promote, rather than inhibit, breast cancer development.
How Does Pregnancy Help Prevent Breast Cancer?
Breasts are developing during puberty, when hormone levels are changing rapidly and body-wide maturation is taking place. Breast tissue cells reach complete maturity after a full-term pregnancy. Your breasts are immature from your first menstrual cycle to your first pregnancy. Researcher Irma Russo, MD, of Fox Chase Cancer Center in Philadelphia believes that limiting the time that breast cells are immature offers the best protection against cancerous changes. A hormone produced during pregnancy, human chorionic gonadotropin (hCG), causes breast cells to mature, and protects against future cancer development. The pregnancy hormone hCG actually causes permanent genetic changes in your mammary glands, and these genetic changes can help prevent breast cancer.
During pregnancy, fetal cells are produced, and those cells may stay in your peripheral circulation for a long time after your pregnancy. The ability of these persistent cells floating about in your bloodstream is called fetal microchimerism (FMc). Research done by Dr. Vijayakrishna K. Gadi of the Fred Hutchinson Cancer Research Center in Seattle (and on the About.com Medical Review board) shows that these fetal cells may help reduce your risk of breast cancer. Fetal microchimerism may cause a protective effect by causing your immune system to be alert for malignant (cancerous) cells to destroy. "We have known for some time that pregnancy can be protective for breast cancer," Gadi said, "but our results help to address the enigma of why not all women are protected." But the researchers are hopeful for future practical application for their results. "With further studies," added Gadi, "we might be able to develop these fetal cells as a form of treatment for breast or even other types of cancers."
Pregnancy Is Not A Guarantee of Protection
Pregnancy cannot, however, offer full protection against breast cancer. It is possible to be diagnosed with breast cancer during pregnancy, and to be treated with chemotherapy. A diagnosis of breast cancer during pregnancy is rare: only one in 3,000 (0.03%) to one in 10,000 (0.01%) pregnant women are found to have breast cancer. There is a very noticeable increase in breast cancers for the first year after pregnancy, which afterward then drops significantly below rates for women who have never been pregnant and never given birth.
Pregnancy and Fertility After Breast Cancer
If you are diagnosed with breast cancer, chemotherapy and follow-up medications such as estrogen supressors and aromatase inhibitors can cause your ovaries to stop working for a while. During this time, you may be temporarily infertile, but if you are not yet menopausal after treatment, your fertility may return 6 to 12 months after chemotherapy is complete. You also have the option of freezing eggs or embryos before you begin treatment. The American Cancer Society website states, “Despite concerns that pregnancy could cause cancer to return, studies to date have not shown this to be true for any type of cancer.” Most breast cancer survivors who wish to have children after treatment worry about the pregnancy’s hormonal changes causing a recurrence, but studies have shown no difference in recurrence for women with or without post-treatment pregnancies.
Sources:
National Cancer Institute. Breast Cancer Prevention. Estrogen (decreased exposure). Last Modified: 10/05/2007.
Karolinska Institutet. Department of Medical Epidimiology, Research. Pregnancy-associated breast cancer. Mats Lambe, project leader. Updated Feb 9, 2007.
Innovations Report. Genetic changes in breast tissue caused by pregnancy hormone helps prevent breast cancer. Irma H. Russo, M.D., of Fox Chase Cancer Center in Philadelphia. Published: 04/ 20/2005.
American Society of Clinical Oncology (ASCO). Fetal microchimerism and breast cancer: A case-control study. V. K. Gadi, et. Al. 2007 Breast Cancer Symposium.
