Answer to Question #3955 Submitted to "Ask the Experts"

I underwent a cardiac stress test last week. Before the test, I was asked if there was any possibility that I could be pregnant. When I responded "yes" they told me I would have to have a blood pregnancy test prior to having the stress test because they would be injecting me with radioactive material during the test. I had the pregnancy test on Wednesday of that week and was told that it came back negative. I had the test on Friday. I believe that I had only been pregnant for a few days and the pregnancy test did not detect that I really was pregnant at the time.

After having the test, I am extremely concerned that I may have harmed the fetus. What damage may have been done to the fetus? What are the risks associated with this type of exposure?

Also, I am an airline pilot. I was wondering if radiation exposure is cumulative and if I should be concerned about being further exposed during flying or are these different types of radiation?

Relax, all the exposures that you have experienced are very low exposures and will not increase your risk for birth defects or miscarriage. The cardiac stress test uses a radioactive agent that demonstrates how well your heart is perfused and whether there is a problem of blood flow to any part of the heart. The exposure to the embryo during that procedure is extremely small. Besides your embryo was very young and in a stage that we refer to as the "all-or-none period." During this stage the embryo is resistant to the malforming effects of radiation because all the cells have the ability to make a normal embryo, so even if the embryo was exposed to a high exposure it will die or have the same risk for normalcy as an unirradiated embryo. But your exposure was so low that there was no risk of killing the embryo. So the cardiac stress test will not change your reproductive risks which are the same for any healthy woman without personal or family reproductive problems, 3% for birth defects and 15% for miscarriage.

As far as the risk of flying, there are no reasons why your embryo is at an increased risk for birth defects. First, the exposure while flying is too low and, secondly, the exposure is protracted (spread over time) which makes its effectiveness much less.

Good luck.

Robert Brent MD, PhD