Because most cases of breast cancer occur in older women, reproduction issues are often not a concern. Women over 50 account for more than 75 percent of all breast cancer diagnoses, according the American Cancer Society (ACS). Still, the ACS reports that nearly 12,000 women under the age of 40 are diagnosed with invasive breast cancer each year. Women who are under the age of 40 have a 1 in 68 chance of developing the disease.

For many of these young women diagnosed with breast cancer, reproduction issues are very much in mind as they enter treatment. If they plan on having children, they may be concerned about whether estrogen levels will encourage the cancer to return, following treatment.

During pregnancy, total estrogen levels are 1,000 times that of a menstruating woman. In the past, physicians advised breast cancer patients that becoming pregnant may pose a serious risk to their lives since estrogen levels are elevated for an extended period of time during pregnancy.

If a tumor is found to be estrogen-receptor positive, then the presence of estrogen may cause any remnants of the tumor to grow. However, most studies have found that a pregnancy after breast cancer does not increase the chances of a recurrence despite the increased estrogen levels. Recent studies on patients with subsequent pregnancies seem to indicate that there is little or no difference in long-term survival rates.

In fact, in one study conducted at The Fred Hutchinson Cancer Research Center in Washington, results revealed that women who became pregnant after treatment had slightly better survival rates and longer disease-free intervals when cases of recurrence were compared against a control group.

The ACS recommends waiting five years before becoming pregnant if the cancer tumors are particularly large or aggressive, or if a number of lymph nodes have had evidence of cancer. In these cases, the cancer has a greater chance of spreading to other areas of the body. When tumors are small and lymph nodes are not involved, the ACS recommends waiting two years following treatment.

Breast cancer patients should consult with their physician regarding their prognosis and how long they should wait before becoming pregnant based on their individual diagnosis and treatment plan. The discussion should include the possibility of recurrence, the possibility of damage to her ovaries from radiation treatment, possible heart damage from chemotherapy drugs and any other health-related matter that could be exacerbated by pregnancy.