Answer to Question #8293 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I had papillary cancer of the thyroid and was given 5550 MBq of 131I. Then I had a diagnostic scan with 185 MBq four months later. My last period was a month after that. Are there any risks of birth defects to my baby due to the radioactivity from these administrations?
I assure you that there is no chance whatsoever of any birth defects in your baby caused by the radioactive iodine. All of it had left your body in less than a week, and your baby's thyroid gland isn't even capable of taking up iodine until 9 to 12 weeks of gestation.
I assume that you are on thyroid replacement pills. As you get to your second and third trimester, you may need a little more thyroid hormone—ask your doctor to check you. After the baby comes, you will go back to your usual dose.
Carol S. Marcus, PhD, MD
Professor of Radiation Oncology and of Radiological Sciences, UCLA