CT use on pregnant women leaps from late 1990s

CT exams are not routinely ordered for pregnant women, but may be necessary to detect suspected life-threatening conditions, such as bleeding in the brain, blood clots in the lungs, or appendicitis. The use of CT to do such studies has grown enormously over the last decade. A study published March 17 in the online edition of Radiology found that CT exams on pregnant women increased 25.3% per year from 1997 to 2006.

What to do when using CT to image pregnant patients is the focus of a presentation early May 19, the opening day of the International Symposium on Multidetector-Row CT in San Francisco, CA. Pregnancy poses a particular issue for CT because of concerns regarding the developing fetus and radiation.

The majority of CT examinations (approximately 75%) analyzed in the study reported in Radiologywere performed in areas of the mother's body separate from the uterus, so the fetus was not directly exposed to radiationn. Still, low levels of radiation have been shown to carry a small risk of harm to a developing fetus.

"Imaging utilization has not been previously studied in the pregnant population," said Dr. Elizabeth Lazarus, assistant professor of diagnostic imaging at the Warren Alpert School of Medicine at Brown University and a radiologist at Rhode Island Hospital in Providence. "This population may be vulnerable to the adverse effects of radiation."

Lazarus and colleagues conducted a retrospective review of nuclear medicine, CT, fluoroscopy, and plain-film x-ray imaging examinations performed at Rhode Island Hospital and Women and Infants' Hospital from 1997 through 2006 to determine how often these imaging exams were performed on pregnant women and the estimated radiation dose to the fetus. The average estimated fetal radiation exposure per exam for CT was 4.3 mGy (milliGray, a unit of absorbed radiation), compared to 2.91 mGy for fluoroscopy, 0.4 mGy for nuclear medicine, and 0.43 mGy for x-rays.

"Women should know that imaging is generally safe during pregnancy and is often used to detect potentially life-threatening problems," Lazarus said. "However, this study should raise awareness about imaging trends in pregnant patients and help us continue in our efforts to minimize radiation exposure."

Increased use of electronic medical records may help physicians and patients keep track of the number and types of imaging tests performed on pregnant women and give proper consideration to alternative imaging tests, such as MRI and ultrasound, that do not expose the patient or fetus to ionizing radiation, she said.