Radiological exams on pregnant women increase by 81% over 10-year period

In 2006, CT pulmonary angiography was the most common CT exam performed on pregnant women.

Utilization rates of radiological examinations in pregnant women rose dramatically over the last decade, driven largely by CT studies of the head and CT pulmonary angiography (CTPA). In one of the first studies to evaluate rates of radiological examinations that expose pregnant women to ionizing radiation, the number of exams per patient population was found to have risen by 81% over the period, according to research presented at the RSNA meeting by Dr. Elizabeth Lazarus of Brown University.

The study looked at radiographic plain film, nuclear medicine, and CT studies performed on pregnant women over 10 years, from 1997 to 2006, at a single academic medical center. MR and ultrasound were not included as they do not impart radiation to the patient. Fluoroscopic and interventional radiology exams were excluded from the study because so few of them were performed on the population during the study period.All imaging examinations that expose pregnant women, including inpatients, outpatients, and emergency department patients, to radiation are recorded in a database at Lazarus' institution. A retrospective review of the database found that 5235 radiology examinations were performed on 3249 pregnant patients over the 10 years.CT utilization rates rose most sharply -- by an average of 25% per year -- Lazarus found. Average growth rates for plain film and nuclear medicine studies were more modest, with utilization of plain film growing by 6.8% and nuclear medicine by 17%, on average.These results could cause some concern, as CT imparts the greatest amounts of radiation to the patient. Exposure to radiation has been linked to such fetal risks as central nervous system defects and increased incidence of childhood leukemia and other malignancies. In addition, pregnant women may be more vulnerable to the adverse effects of increased radiation.CT studies of the abdomen and pelvis impart an average dose of 20 mGy to the fetus, by far the largest average dose of all studies. However, that dose still falls within the medically allowable radiation threshold of 50 mGy.In addition, more than 60% of CT studies performed impart much lower doses of radiation to the fetus. Head studies account for 37% of CT exams, and the approximate radiation dose to the fetus is less than 0.01 mGy. CTPA, which accounts for 27% of CT studies performed on pregnant women, imparts an approximate radiation dose of less than 0.1 mGy to the fetus.Other approximate radiation doses include less than 1 mGy for nuclear medicine studies and for plain-film studies where the fetus is in the beam. When the fetus is not in the beam, the radiation dose to the fetus is less than 0.01 mGy for plain-film studies.Radiation dose to the pregnant woman's breast tissue during exams is another area of concern. According to Lazarus, the approximate radiation dose to the breast during CTPA is 20 mGy, which is equivalent to four mammograms.CTPA was the most common radiological examination performed on pregnant women, Lazarus found.