Since this is a question we are frequently asked, we thought that we'd share an excellent resource on this topic.
This information is excerpted from a post for the Best for Babes Foundation by Dr. Shannon Tierney, Breast Oncology Surgeon at the Swedish Cancer Institute in Seattle, Washington.
- Mammogram CAN be done in a breastfeeding woman. Ideally, it should be done with an experience mammographer who knows the woman is breastfeeding, as the images will be more complex. She should empty her breasts as much as possible right before the mammogram, either by nursing or pumping.
- Ultrasound CAN be done in a breastfeeding woman. Same issues apply. Ultrasound, incidentally, can actually be somewhat useful therapeutically for breaking up a clogged duct.
- MRI CAN be done in a breastfeeding mother, though it is not recommended just for routine screening (as is done in high risk women) because the sensitivity is lowered. Gadolinium, the dye used for MRIs of the breast, barely gets into milk and is not absorbed by the baby’s gut, so it is safe – no need to pump and dump. Milk cytology can be done, but it’s often low-yield. It does have the advantage of being noninvasive, but needs a specialized pathologist and doesn’t usually rule out cancer.
- Needle biopsies (fine needle aspiration and core biopsy) CAN be done in a breastfeeding mother. The smallest needle that will get the diagnosis should be used, but the risk of milk fistula, which is chronic milk leakage, is very rare. There is no research on the incidence of milk fistulas with biopsies, but it’s rare enough that when it happens it gets written up as case reports! Incisions around the areola should avoid the lower outer border to keep from injuring the 4th intercostal nerve, and radial incisions (or an approach similar to what is done for C-sections, where the skin incision is made to be cosmetic and the inner dissection is done in a radial fashion) are recommended. The breast should be kept well drained with nursing or pumping before and after. Use of a local anesthetic like lidocaine is safe – no need to pump and dump.
- Surgery on the breast CAN be done in a breastfeeding mother. Milk fistula is still a risk, though that risk may not be reduced much by weaning as the breast could continue to make milk for months after weaning. The surgeon should be very careful with her technique – minimizing unnecessary damage to the milk ducts and avoiding the central breast if possible. Radial incisions and avoiding the 4th intercostal nerve (see above) are recommended. The breast should be kept well drained with nursing and pumping before and after. Most types of anesthesia will be out of the milk by the time the patient is awake and alert – at most, pump and dump once.