Many drugs used to treat cancer are very toxic and mothers should not breastfeed while taking them. A few considerations regarding newer therapies and times when it may be appropriate to discuss maintaining lactation are noted below. For more information on specific medications and references, please refer to LactMed, e-lactancia, Infant Risk, or Mother to Baby.

There may be situations where it is possible for the lactating parent to pump and dump during parts of their treatment course so they can maintain lactation for at least some of the time between treatments. For example, the lactating individual may be able to pump and discard milk during treatment and for a few days after receiving chemotherapy when it is given intermittently (such as once a month) and then resume breastfeeding for a period of time until they receive the next cycle.

Some newer types of chemotherapy (including kinase inhibitors and monoclonal antibodies) are currently considered to be contraindicated during breastfeeding. The monoclonal antibodies may prove to be acceptable to use during breastfeeding, but very little safety information is available in nursing mothers. Some monoclonal antibodies are conjugated with specific toxins; these should be avoided during nursing.

In addition to the presence of concerning chemotherapeutic agents, physicians and patients should consider the lactating parent’s risk for infections (such as mastitis) due to immune suppression during treatment as well as limitations on their ability to maintain lactation due to fatigue and other side effects related to chemotherapy when making decisions about lactation with individuals undergoing treatment for cancer.