Thyroid Scans in a Breastfeeding Mother

Mother Nursing Infant Son
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There are some times when, as a new mother breastfeeding her baby, you may have thyroid symptoms that cause your physician to recommend a diagnostic thyroid scan. It's important to review some of the issues involved in performing thyroid scans in a woman who is breastfeeding.

A thyroid scan is a test to help evaluate the structure and function of your thyroid. It may be ordered when an overactive thyroid—hyperthyroidism—is suspected. To perform the scan, you receive an injection of a radioactive "tracer" drug, and then imaging scans are performed to evaluate your thyroid function.

What to Do If a Thyroid Scan Is Recommended While You're Breastfeeding

If your doctor suggests a thyroid scan, you can first ask the doctor whether an alternative diagnostic procedure—for example, blood tests, or fine needle aspiration biopsy—can be performed instead of the scan, due to your breastfeeding. The primary reason for a thyroid scan in a nursing mother is to differentiate between postpartum thyroiditis and Graves' disease. In some cases, this may be possible with careful clinical evaluation and blood tests, or ultrasound, all of which are safe for the baby and don't interfere with breastfeeding.

If a thyroid scan is needed, you need to discuss whether you are breastfeeding with your physician. It will also be important for the doctor to know the age of your baby, and if you are exclusively breastfeeding or supplementing with formula, and if you pump and save milk. Also make sure that anyone else involved in the procedure—staff, nurses, radiologists at the location or hospital where a scan might be performed—is informed that you are breastfeeding.

Thyroid scans can be performed while breastfeeding, but not with the typical radioactive drug—radioactive iodine. If radioactive iodine is used, it passes into your breast milk for weeks, and concentrates in your baby's thyroid. This can make the baby hypothyroid. Radioactive iodine is, therefore, never recommended if you plan to continue breastfeeding. If you are breastfeeding and have this test done, you need to stop breastfeeding permanently.

How to Safely Get a Thyroid Scan and Continue Breastfeeding

If a scan needs absolutely needs to be done, and you are exclusively breastfeeding, you will want to pump and save enough milk to feed your baby for a three-day period. You can then plan with your doctor to have your thyroid scan with a substance called technetium, rather than radioactive iodine.

According to breastfeeding expert, Dr. Jack Newman:

"Technetium has a half life (the length of time it takes for half 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 and the mother can nurse her baby without concern about his getting radiation."

Typically, after stockpiling enough milk ahead of the scan, as a nursing mother, you should "pump and dump" her breast milk during the 30-hour period after the injection. You can then resume breastfeeding again after that 30 hour period of pumping milk and disposing of it.

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