Lactation (breast milk production) and breast-feeding should be stopped if surgery or chemotherapy is planned.

If surgery is planned, breast-feeding should be stopped to reduce blood flow in the breasts and make them smaller. Breast-feeding should also be stopped if chemotherapy is planned. Many anticancer drugs, especially cyclophosphamide and methotrexate, may occur in high levels in breast milk and may harm the nursing baby. Women receiving chemotherapy should not breast-feed. Stopping lactation does not improve survival of the mother.

Breast cancer does not appear to harm the fetus.

Breast cancer cells do not seem to pass from the mother to the fetus.

Pregnancy does not seem to affect the survival of women who have had breast cancer in the past.

Some doctors recommend that a woman wait 2 years after treatment for breast cancer before trying to have a baby, so that any early return of the cancer would be detected. This may affect a woman’s decision to become pregnant. The fetus does not seem to be affected if the mother has previously had breast cancer.

Effects of certain cancer treatments on later pregnancies are not known.

The effects of treatment with high-dose chemotherapy and a bone marrow transplant, with or without radiation therapy, on later pregnancies are not known.