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.

close up of dark haired baby breastfeeding
Many medical tests are compatible with lactation and do not require breastfeeding to be interrupted

Breast imaging and biopsies

The Academy of Breastfeeding Medicine (ABM) Protocol #301 refers to guidelines from The American College of Radiology (ACR)2 that say all breast imaging studies and biopsies are safe for breastfeeding women.

Is weaning necessary to investigate breast lumps?

Dr Jack Newman, a Canadian paediatrician and breastfeeding expert, states that it is not necessary to wean prior to diagnostic tests on the breast. He says:

A reminder: almost no investigation of the breast (ultrasound, mammogram, CT scan, MRI scan, needle biopsy, core biopsy, etc.) requires a mother to stop or interrupt breastfeeding. If there is urgency in making a diagnosis, waiting for the mother’s milk to dry up is not rational, since it may take several weeks. Even if there is a reason to stop on the side with the lump, the baby can and should continue breastfeeding on the other side.


Diagnostic X-rays don’t affect breast milk and no special precautions are required.3 Occasionally a contrast agent is used with an X-ray to improve the image quality of the soft tissue e.g. barium may be used, either swallowed or as an enema. As barium is chemically inactive and is not absorbed by the body, breastfeeding is not affected.4


A mammogram is another type of X-ray. Mammograms are compatible with breastfeeding but may be more difficult to interpret on a lactating breast due to the density of breast tissue.5 It is recommended that breasts are as empty as possible prior to the mammogram to maximise the quality of the images67 and that the radiographer has experience of reading images of lactating breasts8.


Ultrasound helps distinguish between fluid filled (cystic) and solid masses by high frequency sound waves used to see inside the breast. Ultrasound is said to be safe to use in lactation (Mitchell et al, 2019; Carmichael et al., 2017; Wilson-Clay and Hoover, 2017). Geddes (2009) discusses particular techniques for ultrasound on a lactating breast in Ultrasound imaging of the lactating breast: methodology and application.  Emptying the breasts prior to a breast ultrasound may maximise the quality of the images (Charlamb, 2017).

Magnetic resonance imaging (MRI)

MRI scans use strong magnetic fields and radio waves to produce clear pictures of the inside of the body. The Academy of Breastfeeding Medicine states that MRI is not contraindicated during breastfeeding:

Although MRI is less sensitive in the setting of lactation due to increased parenchymal density and vascularity, it nevertheless is not contraindicated and may provide diagnostic and treatment planning benefit.

The American College of Radiology (ACR) say:

although not the initial imaging tool of choice, screening breast MRI is not contraindicated during lactation and may be considered in lactating women with a high lifetime risk of breast cancer.

MRI with contrast: Gadolinium

About one in three MRI scans use gadopentetate dimeglumine (Gadolinium) a contrast medium to improve clarity of the images.9 Manufacturers’ package inserts may say that breastfeeding is not recommended for 24 hours after use10, however HalesMeds online [paywall accessed 7 April 2022] explains that Gadolinium has a short half-life (1.6 hours), is poorly absorbed orally and only reaches breast milk in incredibly low levels, therefore, although 24 hours interruption of breastfeeding would eliminate all risk, this seems extreme in the circumstances. Several authorities on the subject say it is not necessary to interrupt breastfeeding after MRI with contrast.11121314

The Academy of Breastfeeding Medicine ABM 2019 explains:

MRI with gadolinium-based intravenous contrast. Gadolinium is a heavy metal incorporated into intravenous contrast agents to enhance vascular structures and organs during MRI. Less than 0.04% of the administered maternal dose is excreted into the breast milk, and <1% of the contrast ingested by the child is absorbed from the GI tract. Therefore, the systemic dosage to the child is <0.0004% of the intravenous dose given to the mother. The ACR states in its published manual on contrast media that it is safe for the mother to continue breastfeeding after the administration of intravenous gadolinium-based contrast.

Dr Jack Newman summarises:

which is more hazardous for the baby, breast milk containing minuscule amounts of contrast media, most of which are not absorbed, or formula, even for only 24 hours? We can say unequivocally that, given the risk of interrupting breastfeeding, mothers should be reassured that they will be doing the best for their babies by not interrupting breastfeeding for even 1 second after MRI, CT, or most other radiologic procedures.

Breast biopsy

A biopsy involves taking a sample of a lump or mass within the breast. Because a biopsy may involve a surgical procedure (incision and removal of tissue) it could pose a risk to breastfeeding now or in the future due to damage to ducts, scarring and risk of infection. Core needle biopsy after a full image work-up is the preferred diagnostic procedure for a breast lump. This is due to its safety, cost effectiveness and precision. However there remains a small risk of infection, milk fistula formation, infection or bleeding (Mitchell et al., 2019) or a risk of developing a milk-filled cyst or galactocele15. Despite these possible complications, a biopsy is compatible with breastfeeding and stopping breastfeeding is not advocated prior to the procedure as this would lead to an increased risk of a fistula (ABM Protocol #30).

What is a milk fistula?

A fistula is an area or “hole” on the skin of the breast that constantly leaks breast milk from a milk duct below. A fistula tends to be a complication arising from a biopsy, abscess or surgical procedure on a lactating breast.16

Avoiding a milk fistula

The ABM and Dr Jack Newman says that the best way to avoid a milk fistula following a biopsy is to continue to breastfeed. Dr Newman explains:

An important factor in preventing a fistula is to continue breastfeeding on that breast. If the mother doesn’t, the milk is likely to find the path of least resistance to flow, which may be this relatively large opening [the biopsy wound]. Often a fistula becomes apparent after the sutures are taken out, so perhaps in the case of the lactating breast, sutures or staples should be left in much longer than usual. Skin glue can be used in addition to sutures or staples when closing the wound.

Should a fistula occur, it can dry up on its own without stopping breastfeeding on that side. If the mother does not want to stop breastfeeding on that side and can tolerate the leaking, there is no harm in leaving the fistula. If it is a problem, stopping breastfeeding on that breast only is an option.

Breasts work individually so if a mother decides to stop breastfeeding on the affected breast, the other side will usually compensate by increasing production. Gradually reducing the number of feeds on the breast with the fistula will give the other breast time to compensate (Newman, p 162). In this situation using medication to reduce milk supply  would affect both breasts so is best avoided. See How to Stop Breastfeeding for more information on reducing production in one breast or both.

Tests with contrast agents

Computed tomography scan (CT or CAT scan)

A CT scan uses a powerful X-ray and computer to create images from inside the body. As part of the procedure special dyes or “contrast agents” may be injected or swallowed to improve image visibility. The agents typically used are iodinated radiocontrast agents. The iodine in these agents stays bound to the molecule preventing it from entering breast milk.1718

The Royal Australian and New Zealand College of Radiologists (RANZCR) says:

Cessation of breast feeding or expression and discarding of breast milk after iodinated contrast media administration are not required

The Academy of Breastfeeding Medicine states:

CT uses a form of intravenous contrast containing highly bound iodine that helps visualize vascular structures and organs. Less than 1% of the administered maternal dose is excreted into the breast milk, and <1% of the contrast ingested by the child is absorbed by the gastrointestinal (GI) tract. Therefore, the systemic dose to the child is <0.01% of the intravenous dose given to the mother. The ACR states in its published manual on contrast media that it is safe for the mother to continue breastfeeding after the administration of intravenous iodinated contrast.

Further information

Further resources discussing CT scanning and whether specific named 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 2021 information sheet from The Breastfeeding Network—a breastfeeding charity in Great Britain. Discusses some named contrast media with further references.
  • ACR Manual on Contrast Media v10.3, American College of Radiology, 2021—Chapter 20 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.

Intravenous pyelogram (IVP)

Intravenous pyelogram (IVP) is another type of X ray using a contrast medium that helps the radiologist check the health of the kidneys, ureters and the bladder. As with CT scans, iodinated compounds are used but they are not radioactive (Newman, 2007).

Breastfeeding and cancer screening

The American College of Radiology (ACR) document Breast Imaging of Pregnant and Lactating Women provides up-to-date information on diagnostic techniques for breast imaging during lactation and pregnancy (diFlorio-Alexander et al, 2018). While Cancer: Diagnostic Tests, Therapeutic Procedures and Treatment while Breastfeeding (LLLI, 2022), by Diana West, IBCLC answers the most commonly asked questions breastfeeding mothers have when faced with testing and treatment for cancer:

Imaging techniques used for diagnosis of breast pathology may include ultrasound, mammogram, magnetic resonance imaging (MRI), positron emission tomography (PET) scan, 2-Methoxy Isobutyl Isonitrile (MIBI) scan, electrical impedance tomography (EIT) scan, computer axial tomography (CAT) scan, thermography, or diaphanography. These techniques are non-invasive and usually do not affect milk production or safety.

It may be more difficult to interpret breast tissue results due to the increased density from lactation, but it is not impossible. Feeding or pumping before the imaging is recommended, to improve the quality and sensitivity of the scan. It is usually not necessary to interrupt or suspend breastfeeding for these procedures with the exception of the PET scan, which requires separation of the breastfeeding dyad for 12 hours, though the milk itself is safe. As always, it is important for the prescribing physician and radiologist to consult reliable updated sources before the imaging.

Breastfeeding during chemotherapy is absolutely contraindicated because the medications used to eradicate cancer are highly toxic and transfer into milk. Breastfeeding after chemotherapy has been completed may be possible, either by relactation or as a result of another pregnancy, depending upon the drugs that were used.

Breast cancer mutation and screening

Carmichael et al discusses breast cancer screening in women who have breast cancer mutations and are pregnant or breastfeeding (Carmichael, 2017). Their summary includes:

  • Encourage all women to breastfeed as it can reduce their risk of breast cancer and has many health benefits for the breastfed baby
  • Recommend breast awareness and a clinical breast examination every six months in women with BRCA (breast cancer) mutations who are breastfeeding
  • If a woman has never had breast screening or is outside the recommended interval between screenings, recommend she have a breast MRI if she intends to continue breastfeeding.

Breastfeeding after breast cancer treatment

  • Radiation therapy to the breast can damage mammary tissue affecting future milk production in that breast and may also affect the elasticity of the nipple.19 One study in 1995 found that only one in four women could breastfeed successfully on the treated breast after conservative surgery and radiation therapy.20 In another small study of breastfeeding after radiation therapy, patients noted an absence of breast growth during pregnancy, 55% breastfed from the treated breast but milk volume was significantly lower in most of the patients.21 Leal et al found that although breastfeeding is possible in at least half of women after radiotherapy, it is in reduced volume.22
  • Breast surgery such as a lumpectomy will also have an impact on the initiation of breastfeeding depending on how many ducts and nerves were severed, scar tissue and the position of the incision on the breast.23 For more information on how surgery can affect breastfeeding see Breast Surgery and Breastfeeding which includes information on maximising milk supply after any surgical procedure on the breast.
  • One sided nursing. If a milk supply is low on the treated breast, mothers can be reassured that it is possible to breastfeed with one breast as this breast will increase production and compensate for the other side. In the same way mothers of twins or triplets or those tandem feeing an older sibling produce enough milk for two or three nurslings.
Mother sits on bench with toddler
X-rays, MRIs, CT scans, Intravenous Pyelogram (IVP), ultrasound and mammograms do not affect breast milk

Breastfeeding after radiopharmaceuticals and radioisotopes

Some medical diagnostic tests require the use of radiopharmaceuticals. Radiopharmaceuticals are radioactive drugs that use different radioisotopes (unstable elements that emit radiation) e.g. a lung VQ scan, renal, marrow or bone scan. Radioisotopes may require stopping breastfeeding for a short time to avoid exposing a baby to excess radioactive material. The period of interruption will depend on the type of radioactive substance used, and 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. A good resource for further reading is ABM Clinical Protocol #31: Radiology and Nuclear Medicine Studies in Lactating Women.

Technetium 99M

In Breastfeeding and Radioactivity, iLactation online conference 2013, Veronica Garea, Head of the Department of Safety and Environmental Impact (INVAP), stated that the preferred radioisotope for a breastfeeding mother is Technetium 99 metastable (Tc-99m). discuss that although the radioactive half-life of Tc-99m is fixed at six hours the American Academy of Pediatrics (AAP) and the International Commission on Radiological Protection recommend different time periods to stop breastfeeding or store breast milk depending on which formulation of Tc-99m is used. The time specified to abstain from breastfeeding to avoid risk to the breastfed baby may be less than 30 hours (five half lives); eg some formulations may require cessation of breastfeeding for four hours while others require 12–24 hours interruption. For those who prefer a conservative approach, Hale recommends storing breast milk for 30 hours post procedure after which time the stored milk will be safe to use.[paywall][/ref]24

The Academy of Breastfeeding Medicine lists recommended times for stopping breastfeeding for many different Technetium-99m imaging agents in ABM Clinical Protocol #31: Radiology and Nuclear Medicine Studies in Lactating Women (2019).

VQ Scans and breastfeeding

A lung scan or ventilation-perfusion (VQ) scan is a diagnostic test that uses radiopharmaceuticals to check for a blood clot in the lungs (pulmonary embolism).25 Inside Radiology recommends interrupting breastfeeding for 24 hours after this type of scan:

Women who are breast-feeding need to make special preparations for after the scan. This will involve stopping breast-feeding for approximately 24 hours. This is due to the radioactivity in your breast milk after the scan injection. You should discuss this with your referring doctor or with the nuclear medicine practice where you will be having the test. You might need to have bottles of formula or previously expressed breast milk available.

The Academy of Breastfeeding Medicine discusses a 12 hour interruption for the specific perfusion agent Tc-99m MAA;

For Tc-99m MAA, 12-hour interruption is recommended. Although no interruption is required for the ventilation agents Tc-99m DTPA or xenon gas, a 12-hour interruption is recommended for all VQ scans because these agents are always used in conjunction with the perfusion agent Tc-99m MAA. During interruption, patients should express breast milk every 3–4 hours for 10–15 minutes or until minimal milk flows. The milk expressed can be stored refrigerated and given to the infant after 10 physical half-lives, or 60 hours, have elapsed.

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 their own thyroid gland function or future risk of thyroid cancer and increase the mother’s radiation exposure in the breast tissue (HalesMeds 2022; Mitchell et al, 2019).

Use of breast milk following radiopharmaceuticals

When a radiopharmaceutical is given to a breastfeeding mother, radioactivity can be absorbed into breast milk which could pose a risk to the baby. Expressing breast milk after the procedure will maintain the mother’s milk supply and reduce the mothers radiation exposure due to the milk concentrated in her breasts. The radioactivity of expressed and stored breast milk will gradually dissipate so that this milk could still be used after a suitable waiting period. How long breast milk will need to be stored so any radioactivity is at safe levels, depends on the radioisotope that has been used and it’s individual half-life (the time needed for the amount of the drug in the body to be reduced by half). 26

Milk storage times

The ABM Clinical Protocol #31: Radiology and Nuclear Medicine Studies in Lactating Women discusses storage times required with some of the common isotopes used in medical tests. Storage times range from no interruption to breastfeeding needed, to waiting for ten half lives/approximately 60 hours for some agents. The Nuclear Regulatory Commission (NRC) (2018) and International Commission on Radiological Protection (ICRP)27 have published guidelines for the most commonly used radiopharmaceuticals.

Precautions for breastfeeding and physical contact after radioisotopes

Inside radiology describes the precautions following radioisotopes:

  1. Interrupt breastfeeding as directed by the medical team to give time for the radioactivity to reduce to an acceptable level. Any breast milk pumped during this period can be stored in the fridge or freezer for use after the restriction period.28
  2. Minimise close contact with children after the procedure for the same specified period of time as in #1 above, keeping a distance of 2-3 metres between parent and child where possible (Cain, 2018) taking account of the children’s emotional needs:

it is important to remember the emotional needs of the child. If the child needs a cuddle then this should occur. The child can be touched or kissed, but if another carer is available to comfort the child, then this would be preferable. If the child is happy and/or content, then a safe distance of 2–3 metres should be maintained between the child and the person who received the radiopharmaceutical.

Good resources for looking up compatibility of radioactive materials in medical tests while breastfeeding, and how long breastfeeding should be interrupted include:


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 breast milk. 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.

This article should not be construed as medical advice. Always check with your medical professional for the latest guidance on compatibility of medical procedures with breastfeeding.

**Excerpts reproduced by permission of Pinter and Martin.