Radiology and nuclear imaging

Can I breastfeed if I need a special X-ray or a radioactive test?

Many tests, including X-rays, ultrasound, mammograms, and MRIs, generally do not affect breastfeeding. Some of them use dyes that may be injected into a breastfeeding mother, but the baby’s bowel only absorbs a small amount of them. Some kinds of nuclear imaging require mothers to take radioactive chemicals called radioisotopes. With these, there is a potential risk of cancer or other problems when the baby is exposed to radiation. The amount of radioactivity in breast milk depends on several factors, including the type and amount of radioisotope used and the speed at which it decays.

A) Describing diagnostic agents

Mothers may need certain tests to ensure no disease is present or assess the extent of existing illness. Such tests may involve the use of certain chemicals (diagnostic agents).

Recommendations for diagnostic agents used in breastfeeding mothers may change. Please discuss any concerns with your health-care providers and consider using additional resources for more information.

B) Safe tests

X-rays, ultrasound, mammograms, computed tomography (CT)and magnetic resonance imaging (MRI) are unlikely to affect breastfeeding or the baby.

Some radiological examinations give better results when a diagnostic agent is used. Iodine-based dye is injected into a vein to improve X-rays and CT images, and gadolinium injected into a vein enhances MRI images.

These diagnostic agents enter breast milk in low amounts and furthermore, the baby’s gut only absorbs a small amount of them (NIH). A baby can continue to breastfeed or otherwise drink breast milk if the mother is given these dyes for a test (ACOG 2017; ACOR 2017).

In a few patients, thyroid hormone levels drop or rise after they receive iodine-based dye (Health Canada 2017; Hsieh 2015; Lee 2015). This effect is more likely in individuals who already have thyroid disease. Changes in thyroid hormone levels may affect milk production in breastfeeding mothers.

C) Radioactive materials

In some tests, such as nuclear medicine imaging, breastfeeding mothers receive radioactive chemicals (radioisotopes). Their babies receive the same chemicals from breast milk or are exposed to radiation directly from the mother’s body. There is a potential risk of cancer due to damage to the baby’s genes when babies are exposed to radioisotopes.

Breast milk generally contains less than 10% of the dose the mother has been given (Stabin 2000). Recommendations on breastfeeding depend on the amount of radioactivity in the milk (Leide-Svegborn 2016; Stabin 2000) which varies with (ACOG 2017):

  • Which radioisotope is used.
  • How much is used.
  • How long ago it was given.
  • How fast the mother’s body can eliminate it.
  • How fast the radioactivity stops.

For example, I-123 use requires mothers stop breastfeeding for up to three weeks (Mitchell 2019).

I-131 is used to treat thyroid cancer. It is not compatible with breastfeeding. 


American Congress of Obstetricians and Gynecologists (ACOG) Committee on Obstetric Practice. Committee Opinion No. 723 Summary: Guidelines for Diagnostic Imaging During Pregnancy and Lactation. Obstet Gynecol. 2017 Oct;130(4):e210-e216
American College of Radiology (ACOR). Administration of contrast media to breastfeeding mothers. ACR Manual on Contrast Media. [Place unknown]: American College of Radiology 2017:10.3; 101-102
Health Canada, Recalls and Alerts. Iodinated Contrast Media - Potential Risk of Hypothyroidism. Ottawa: Health Canada; 2017 Apr 4 [cited 2017 Sep 17]
Hsieh MS, Chiu CS, Chen WC, et al. Iodinated Contrast Medium Exposure During Computed Tomography Increase the Risk of Subsequent Development of Thyroid Disorders in Patients Without Known Thyroid Disease: A Nationwide Population-Based, Propensity Score-Matched, Longitudinal Follow-Up Study. Medicine (Baltimore). 2015 Dec;94(50):e2279
Leide-Svegborn S, Ahlgren L, Johansson L, et al. Excretion of radionuclides in human breast milk after nuclear medicine examinations. Biokinetic and dosimetric data and recommendations on breastfeeding interruption. Eur J Nucl Med Mol Imaging. 2016 May;43(5):808-21
Mitchell KB, Fleming MM, Anderson PO, et al. ABM Clinical Protocol #30: Radiology and Nuclear Medicine Studies in Lactating Women. Breastfeed Med. 2019 Jun;14(5):290-294
Stabin MG, Breitz HB. Breast milk excretion of radiopharmaceuticals: mechanisms, findings, and radiation dosimetry. J Nucl Med 2000;41(5):863-873.
United States National Institute of Health (NIH). National Library of Medicine, Toxnet, Drugs and Lactation Database (LactMed) [Internet]. Bethesda: U.S. National Library of Medicine; [date unknown] [cited 2018 Oct 10]