Answer to Question #1627 Submitted to "Ask the Experts"

Q

I am 37 weeks pregnant. One of my coworkers has hyperthyroidism and she started the radiation therapy by taking radioactive iodine. Her doctor told her the radiation would affect adults for one week and affect children for two weeks. She stayed home for one week and came back to work the second week. I don't know if I need to avoid her the second week or for a longer time since it might have an impact on the child. She also mentioned she would have to flush the bathroom using some medicine the first week. Since we will use the same bathroom in the second week and she will use the medicine, shall I be careful about this? I worry about how that will affect my unborn baby.

A

The advice to your coworker given by her physician is standard advice, but the question that you ask me can only be answered definitively if I know the amount of radioactive iodine your coworker was administered and her radioiodine uptake percent. Since you obviously do not have this information, I can only give you a generic response. The radiation therapy to your coworker is predominantly internal radiation to her thyroid which will not affect you. You are exposed to very small amounts of radiation that her body emits. The dose that you would receive diminishes drastically as you distance yourself from her. Do you work in the same room? I do not want to promote anxiety in you because if I had the quantitative information it would most likely reveal that even if you worked at the next desk, your fetus would receive an insignificant exposure. Remember you are 37 weeks pregnant so even a very, very high dose of radiation cannot make birth defects at this stage. The simplest procedure for you to follow is to stay at least 15 feet away from her and you will receive no meaningful exposure.

Robert Brent, MD, PhD