Being told to have a scan while breastfeeding can raise an immediate question: will anything from the examination reach the baby through breast milk?
For most common scans, breastfeeding can continue as usual. The important exception is nuclear medicine, where the advice depends on the exact radioactive tracer used.
X-rays, mammograms, ultrasound, and MRI without contrast
X-rays used for imaging do not remain in the body or make breast milk radioactive. Ultrasound uses sound waves, while MRI uses a magnetic field and radio waves.
These examinations do not normally require you to express and discard milk. You can usually feed your baby before and after the scan.
CT and MRI contrast
CT contrast is usually iodine based. MRI contrast is usually gadolinium based. Only a very small amount enters breast milk, and the baby's gut absorbs only a small part of that amount.
Current guidance supports continuing breastfeeding after standard intravenous CT or MRI contrast. A routine 24-hour interruption is not required.
If you are still worried, tell the radiology team before the injection. They can explain the specific contrast being used and help you make an informed choice. Do not interrupt feeding for longer than advised without discussing how to protect your milk supply.
Nuclear medicine needs tracer-specific advice
Nuclear medicine examinations, including some thyroid, bone, kidney, heart, and PET scans, use a radioactive tracer. Different tracers remain in the body for different lengths of time.
You may be advised to pause breastfeeding for a few hours, for longer, or in uncommon cases to stop breastfeeding that child. The instruction must come from the nuclear medicine team because a general rule is not safe enough.
Tell the team that you are breastfeeding when the scan is being planned, not only when you arrive. This gives you time to express milk beforehand if an interruption will be needed.
The bottom line
Most X-ray, ultrasound, CT, and MRI examinations do not require you to stop breastfeeding, including standard CT and MRI contrast injections. Nuclear medicine is different, so confirm the exact tracer and the time at which breastfeeding can safely resume.