There is no contraindication to undergoing ultrasound- guided core needle breast biopsy, stereotactic core needle biopsy, or MRI-guided biopsy while breastfeeding, and there is no need to interrupt or stop breastfeeding before or after the procedure.¹

Because stereotactic and MRI-guided biopsies use a larger gauge needle², remove more underlying parenchyma, and produce a larger skin defect, the theoretical risk of milk fistula may be higher.  However, the risk of milk fistula remains very uncommon and is only documented in limited case reports in the literature.^3,4 A large cohort of pregnancy-associated breast cancer (PABC) patients demonstrated no milk fistula, even after surgical procedures.⁵ We recommend removing milk per the lactating person’s usual schedule through either breastfeeding or pumping after a biopsy to promote physiologic drainage through the nipple and away from the biopsy site. We do not recommend feeding or pumping more than usual as this will stimulate supraphysiologic milk production.⁶ Temporary low-volume drainage lasting several days is normal and expected after a biopsy.  Milk may be blood-tinged, but it is safe to continue feeding this milk.

Lidocaine, a local anesthetic used during breast biopsy is considered safe with breastfeeding after intravenous, epidural, and high doses as a local anesthetic.  While there is no data on small volume injection used locally in the breast, lidocaine has poor oral absorption so there is no indication to interrupt breastfeeding.⁷ Epinephrine, a local anesthetic that may be used in conjunction with lidocaine, has no available data in breastfeeding.  However, it also has poor oral bioavailability and therefore is unlikely to necessitate interruption in breastfeeding.⁸ For more information about the use of local anesthetics, see the article on Anesthesia.

For more detailed information and references on specific medications that may be used in the perioperative period, please see the section on Anesthesia or refer to LactMed, e-lactancia, Infant Risk, or Mother to Baby.