WASHINGTON, Nov. 27 (Xinhua) -- The past decade has seen an unprecedented increase in the use of radiologic exams on pregnant women, according to a study presented Tuesday at the annual meeting of the Radiological Society of North America (RSNA).

    "Through medical imaging examinations, we are exposing pregnant women to twice the amount of radiation as we did 10 years ago," said Elizabeth Lazarus from Brown University in Rhode Island. "Overall, the levels of radiation to which we are exposing pregnant women are low, however even low levels of radiation have been shown to carry a small risk of harm to a developing fetus."

    The researchers conducted a retrospective review of selected imaging examinations -- nuclear medicine, computed tomography (CT)and plain-film x-rays -- performed at Brown to determine how often these imaging exams were utilized in pregnant women and the estimated resulting radiation dose to the fetus. Data were compiled for the years 1997 through 2006 and compared to the number of infant deliveries per year.

    They found that from 1997 to 2006, the number of imaging studies performed on pregnant women increased by 121 percent. The greatest increases were in the number of CT exams, which deliver more radiation than many other radiologic procedures.

    CT is not routinely used in pregnancy, but pregnant women may undergo CT to detect suspected life-threatening conditions such as bleeding in the brain, blood clots in the lungs or appendicitis.

    The average estimated fetal radiation exposure for CT was 0.69 rads, compared to 0.04 rads for nuclear medicine and 0.0015 rads for plain-film x-rays.

    Dr. Lazarus cautioned healthcare consumers to be aware of this trend. "I want to assure patients that CT can be a safe, effective test for pregnant patients," she said. "However, there are alternatives that should at least be explored. Pregnant patients should ask their doctors about other imaging or diagnostic tests that may not expose the fetus to radiation."