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Radiation protection of pregnant women in therapeutic nuclear medicine

» Can the patient become pregnant after radionuclide therapy, or father a child?

After radionuclide therapy, a female patient should be advised to avoid pregnancy for the period of time indicated in the table below. 
This is to ensure that the dose to a conceptus/foetus would probably not exceed 1 mGy (the member of the public dose limit). Potential spermatozoa damage in male patients is also allowed for in the case of iodine-131.

Suggested time period during which pregnancy should be avoided following radionuclide therapy

Radionuclide
and formFor treatment
ofAll activities
up to
(MBq)Avoid
pregnancy
(months)
I-131 iodide Hyperthyroidism 800 4
I-131 iodide Thyroid cancer 6000 4
I-131 MIBG Neuroendocrine tumours 7500 3
P-32 phosphate Myeloproliferative 200 3
Sr-89 chloride Bone metastases 150 24
Y-90 colloid Radiation synovectomy 400 0
Y-90 colloid Malignancy 4000 1

» Can a patient breast feed a child after therapy?

Many radionuclides used in radiopharmaceuticals can appear in the breast milk of a nursing mother. This represents a potential radiation hazard to the newborn child. The principal risk to the child will be induction of cancer, and is considered to be a factor of two to three times higher than for the average population.

Many diagnostic radiopharmaceuticals clear rapidly from the body, and have radionuclides with a gamma emission only, and a short half-life. Therapy radionuclides, on the other hand, are designed to damage the target tissue, and often have particulate emissions (usually beta particles) and a longer half-life, in order to accomplish this aim.

Any therapeutic radiopharmaceutical administered orally, intravenously or arterially is potentially hazardous to the child, and breast feeding must cease. Intracavitary administrations of suspended particles such as yttrium-90 silicate represent little hazard; however, it would still be wise to cease feeding.

In particular, iodine-131 therapy is an absolute contra-indication to breast feeding. Another contraindication to breast feeding after therapy is the necessary proximity of the child to the mother, which represents an external radiation hazard.

» What if there are pregnant persons near, or living with, the patient?

If the patient has been treated with a gamma-emitting radionuclide, it may be advisable for pregnant women to either not visit the patient for a week following discharge, or to remain at a distance of at least one meter for this period of time. In cases where this is an important consideration, it should be included in the specific therapy discharge guidelines.