We do not want babies to get radioactivity, but we rarely hesitate to do radioactive scans on them. When a mother gets a lung scan, or lymphangiogram with radioactive material, or a bone scan, it is usually done with technetium (though other materials are possible). Technetium has a half life (the length of time it takes for 1/2 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. 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 after most radioactive scans, the mother can continue breastfeeding, but if she and her physician are truly concerned, waiting 2 half lives is enough, for a material such as technetium. Note that if the mother is getting the scan during the first few days after the baby's birth, the baby will get much less because the baby gets much less milk during this time. During this early period, I believe no interruption of breastfeeding is necessary or desirable. Colostrum is desirable for the baby.
If you decide that interruption of breastfeeding is the best course to follow, then express milk for several days in advance (if you have advance warning about the test). Only occasionally is a radioactive scan that urgent that it cannot be delayed for a few days.
Thyroid scans are different. Radioactive iodine is concentrated in milk and will be ingested by the baby and it will go to his thyroid where it will stay for a long time. This is definitely of concern. So, the mother will have to stop breastfeeding? No, because often the test does not need to be done. Differentiating postpartum thyroiditis from Graves' Disease (the most common reason for doing the scan in nursing mothers) does not require a thyroid scan. Get more information from the clinic. If a scan needs to be done, it is possible to do a thyroid scan with technetium.
Revised January 2000
Written by Jack Newman, MD, FRCPC
Used with permission.
