The following information pertains to reproductive risks of radiation exposures to women who are pregnant and have questions about the risk of birth defects and miscarriage. It is also for men and women who are concerned about radiation exposures they have had that might impact the development of their sperm or their eggs (ova) and their risk of genetic diseases because of the radiation exposure. The next few paragraphs are some basic concepts as an introduction to help understand the more specific information provided later. It must be remembered, however, that every healthy woman without personal or a family history of reproductive or developmental problems begins her pregnancy with a 3 percent risk for birth defects and a 15 percent risk for miscarriage. These are background risks for all healthy pregnant women.
Ionizing radiation is the kind of electromagnetic radiation produced by x-ray machines, radioactive isotopes (radionuclides), and radiation therapy machines. There is potential for the embryo or fetus to be exposed during the diagnostic or therapeutic procedures for women who are pregnant and have x rays, fluoroscopy, or radiation therapy or are administered liquid radioactive materials. To determine the risks of a radiation exposure, it is best to request a consultation from a health physicist who works at or consults for the organization where the procedures were performed. In many instances, an evaluation of the radiation exposure would not be necessary because the radiological procedure did not expose the developing embryo.
Most diagnostic procedures expose the embryo to less than 50 mSv.1 This level of radiation exposure will not increase reproductive risks (either birth defects or miscarriage). According to published information, the reported dose of radiation to result in an increased incidence of birth defects or miscarriage is above 200 mSv.
Another important consideration is the stage of pregnancy in which the radiation exposure occurred:
In the first two weeks postconception or the second two weeks from the last menstrual period, the embryo is very resistant to the malforming effects of x rays. The embryo is, however, sensitive to the lethal effects of x rays, although doses much higher than 50 mSv are necessary to cause a miscarriage.
From the third to the eighth week of pregnancy, the embryo is in the period of early embryonic development but is not affected with either birth defects, pregnancy loss, or growth retardation unless the exposure is substantially above the 200 mSv exposure.
From the eighth to the fifteenth week of pregnancy, the embryo or fetus is sensitive to the effects of radiation on the central nervous system. But here again, the exposure has to be very high. The threshold has been estimated to be higher than 300 mSv before an effect can be seen on the IQ of the developing embryo. General diagnostic studies do not reach these levels and, therefore, these effects are rarely of concern for patients.
Beyond the 20thweek of pregnancy, when the fetus is completely developed, it has become more resistant to the developmental effects of radiation. In fact, the fetus is probably no more vulnerable to many of the effects of radiation than the mother in the latter part of pregnancy. But the most important thing is that practically none of the diagnostic radiological procedures will affect an embryo at this late stage of pregnancy and certainly there is no risk for birth defects or miscarriage from the range of exposures that occur from diagnostic studies.
The reproductive risk of nonionizing radiation, which includes electromagnetic fields emitted from computers, microwave communication systems, microwave ovens, power lines, cellular phones, household appliances, heating pads and warming blankets, airport screening devices for metal objects, and diagnostic levels of ultrasound, has been studied extensively. Two national committees of scientists evaluated the risk from these nonionizing radiation sources. Both of the committees published books on the subject. The first came out in 1993 from the Oak Ridge Associated University panel created by the White House while the second was the product of the committee of the National Academy of Sciences. Both of these groups concluded that the reproductive risk of nonionizing radiation is minimal if even existent.