Medical Tests While Breastfeeding

Mothers are sometimes told they need to interrupt breastfeeding in order to have certain medical tests, however many medical tests are compatible with breastfeeding. This article shares useful resources to discuss with your health professionals regarding the compatibility of various diagnostic tests while breastfeeding.

X-rays, MRIs, CT scans, ultrasound and mammograms

X-rays, MRIs, CT scans, Intravenous Pyelogram (IVP), ultrasound and mammograms don’t affect breast milk or breastfeeding so there is no need to interrupt breastfeeding at all 1 2.

Can I breastfeed after a CT scan with contrast?

Three useful resources discussing CT scanning and whether specific contrast media are compatible with breastfeeding are:

  • Breastfeeding and the Use of Contrast Dyes for Maternal TestsClinical Lactation, 2011, by Kay Hoover IBCLC. Comprises a comprehensive list of contrast agents and concludes that a mother can breastfeed after a CT scan with one exception—Teslascan (Mangafodipir Trisodium).
  • Computed Tomography (CT) Scans; a 2015 information sheet from The Breastfeeding Network—a breastfeeding charity in Great Britain. Discusses some named contrast media with further references.
  • Manual on Contrast Media v10.2, American College of Radiology, 2016—Chapter 18 discusses the use of iodinated or gadolinium-based contrast media in breastfeeding women. The authors conclude that such a small percentage of contrast media is excreted into breast milk and absorbed by the baby’s gut that it is safe to continue breastfeeding.

Breastfeeding and cancer

In Cancer and Breastfeeding (Breastfeeding Today, 2011), Diana West, IBCLC answers the most commonly asked questions breastfeeding mothers have when faced with testing and treatment for cancer including; imaging techniques, needle aspiration, biopsy, radioactive isotopes, radiation therapy, chemotherapy and anaesthesia.

Mother sits on bench with toddler

Can I breastfeed after radioisotopes?

Some medical diagnostic tests require radioactive substances e.g. a lung VQ scan, renal, marrow or bone scan. Radioisotopes may require stopping breastfeeding for a short time to avoid exposing your baby to excess radioactive material. The period of interruption will depend on the type of radioactive substance used, the dosage and age of your baby. The mother will need to pump regularly during any interval to avoid mastitis or a drop in her milk supply. If a mother has sufficient expressed breast milk already stored prior to the test, this can be fed to her baby during this waiting period. See below for information on whether the milk pumped during the break in breastfeeding can be used after a waiting time or whether it should be thrown away.

Iodine 131 treatment

If radioactive iodine I-131 treatment is required (e.g. for thyroid cancer or hyperthyroidism) breastfeeding mothers are advised to stop breastfeeding and wean before treatment. Iodine-131 concentrates in the thyroid gland as well as breast milk and breast tissue. Exposing a baby to this breast milk could affect his own thyroid gland and increase the mother’s risk of breast cancer from the additional radiation exposure concentrating in the breast 3 4 5.

Radioisotopes for a breastfeeding mother

In Breastfeeding and Radioactivity, iLactation online conference 2013, Veronica Garea, Head of the Department of Safety and Environmental Impact (INVAP), said that the preferred radioisotope for a breastfeeding mother is Technetium 99 metastable (Tc99m).

Jack Newman explains how long technetium remains in the body:

Technetium has a half life (the length of time it takes for ½ of all the drug to leave the body) of 6 hours, which means that after 5 half lives it will be gone from the mother’s body. Thus, 30 hours after injection all of it will be gone (well 98% will be gone) and the mother can breastfeed her baby without concern about his getting radiation. But does all the radioactivity need be gone? After 12 hours, 75% of the technetium is gone, and the concentration in the milk very low. I think that waiting 2 half lives is enough, for a material such as technetium. But: Not all technetium scans require stopping breastfeeding at all (HIDA scan, for example). It depends on which molecule the technetium is attached to.

How long do I have to stop breastfeeding after a scan with a radioisotope?

This depends on the radioisotope. Good resources for looking up compatibility of radioactive materials in medical tests while breastfeeding, how long breastfeeding should be interrupted and whether to limit physical contact with your baby after the procedure include:

Can breast milk pumped during the waiting time still be used?

Advice varies on whether milk pumped during the time breastfeeding is interrupted for a diagnostic test should be stored to ensure the radioactivity has dissipated, or whether it should be thrown away. In the example of Technetium 99M there is currently a discrepancy between the online information at Medsmilk and the 2014 printed version. Online, Hale and Rowe recommend waiting five half lives (30 hours) before using breast milk following exposure to TECHNETIUM 99m whereas their printed book says “pump and dump for a minimum of 48 hours”. It is not clear which of these is their preferred advice.

For a more conservative approach, breastmilk pumped between 0 and 5 half-lives (30 hours) after the procedure may be stored until radiodecay is effectively complete at 30 hours post-procedure. The stored milk should be safe to use after this period.

Lactmed says:

The milk that is pumped by the mother during the time of breastfeeding interruption can either be discarded or stored refrigerated frozen and given to the infant after 10 physical half-lives, or about 60 hours, have elapsed. Mothers need not refrain from close contact with their infants after usual clinical doses.

In Use of Radioisotopes (and Other Imaging Agents) During Lactation Kelly Bonyata says the milk stored in the waiting period after a diagnostic test with a radioisotope can be used after five half lives have passed:

You do not need to dump this milk. It can be dated, frozen and used after 5+ half-lives of the radioisotope have passed (after 5 half-lives, 96.9% of the radiation is gone; after 10 half-lives, 99.9% of the radiation is gone). You may also get your milk checked for radiation by your radiology/nuclear medicine department.


Many medical tests are compatible with lactation and do not require breastfeeding to be interrupted. X-rays, MRIs, CT scans, Intravenous Pyelogram (IVP), ultrasound and mammograms do not affect breastmilk. Radioisotopes however, may require interrupting breastfeeding for a short time to avoid exposing a baby to excess radioactive material. Information for best practice for different radioisotopes is available online to discuss with your health professionals.