The number of CT scans used to examine pregnant women has grown nearly fourfold in the United States since 1996. File Photo by ylerlson/Shutterstock

July 24 (UPI) -- Over the last 21 years, the use of CT scans during pregnancy has skyrocketed, putting expectant mothers and unborn children at risk for serious health conditions, a study says.

The number of CT scans used to examine pregnant women has grown nearly fourfold in the United States since 1996, according to research published Wednesday in JAMA Network Open.


"We were interested in looking at trends in medical imaging of pregnant women across multi-sites in the United States," Marilyn L. Kwan, a researcher at Kaiser Permanente Northern California and study co-author, told UPI. "CT scans can deliver high doses of ionizing radiation, a known carcinogen, which can cause birth defects, developmental delays and cancer risk."

The study included data for 2.2 million pregnant women who had 3.5 million live births at six integrated health care systems in the United States and Canada between 1996 and 2016. The researchers examined use of various advanced medical imaging that included CT scans, radiography, angiography/fluoroscopy, nuclear medicine and MRI.

All of these imaging methods except MRIs expose patients to ionizing radiation.

The study revealed CT scans were used in nearly 1 percent of all U.S. pregnancies in that 21-year period.

While the use of CT scans on pregnant women rose during that time, the practice began to taper off beginning in 2010.

RELATED Benzodiazepines may raise miscarriage risk early in pregnancy

Doctors most often use ultrasound exam, which involves no ionizing radiation, to monitor fetus growth inside of a pregnant woman. CT scans are sometimes used to pick up more serious conditions such as appendicitis, aneurysm, brain trauma and pulmonary embolism, the researchers say.

Much of that radiation exposure is blocked from the fetus by the mother's uterus and surrounding tissue, according to the Centers for Disease Control and Prevention. The fetus is, however, sensitive to any radiation exposure higher than 0.1 gray.

One study showed that a fetus is most sensitive to radiation exposure between eight and 15 weeks of gestation.

Kwan and her colleagues have now turned their focus to new research exploring possible risks of imaging and childhood cancer.

"I think it's important to be aware of the benefits and harms of imaging, particularly CT scans, and for patients to be smart about it," Kwan said, "to always ask their physician or clinical provider if it's medically necessary to have any imaging test that involves ionizing radiation."