A new study published in the Journal of the American Medical Association using data from Northern California Kaiser Permanente sites suggests that the use of radiation-laden CT scans on pregnant women increased over a 21-year period, despite potential risks to fetal development.
The study examined 3.4 million pregnancies in 2.2 million women and found that in the United States, there were two CT scans for every 1,000 pregnancies in 1996, but that number had jumped to 9.3 for every 1,000 pregnancies by 2016.
In Canada, the rate of increase was slower, going from two CT scans per 1,000 pregnancies in 1996 to 6.2 per 1,000 pregnancies in 2016.
Diana Miglioretti, a co-lead author of the study and a biostatistics professor at UC Davis, said CT scans are commonly used in the medical field because they can quickly provide clear images, but can have up to 100 times more radiation exposure than an X-ray.
“There’s a tradeoff,” Dr. Rebecca Smith-Bindman, the study’s senior author and UC San Francisco radiology professor, said in a prepared statement. “CT scans provide the clearest images, they can be done quickly and are less expensive and more widely available. However, CT scans have the most ionizing radiation and they are commonly done in places of the body where the fetus is exposed to the radiation.”
Across the 21-year period, 5.3 percent of pregnant women studied in the U.S. underwent ionizing radiation imaging, while 3.6 percent of pregnant women in Canada underwent the same. Of these, 0.8 percent in the U.S. and 0.4 percent in Canada underwent CT scanning.
“It is widely acknowledged that ionizing radiation exposure is associated with potential carcinogenic, teratogenic, and mutagenic health risks to the developing fetus. These health risks can translate into congenital abnormalities, developmental delays, and cancer,” the study said. “Imaging rates during pregnancy should be monitored to avoid unnecessary exposure of women and fetuses to ionizing radiation.”
The study noted that an abdominal CT scan on a pregnant woman delivers a dose of ionizing radiation to the fetus similar to that linked to an increased risk of childhood leukemia.
“The risk to any one individual is still very, very low,” Miglioretti said. “We start getting worried when we’re imaging millions of women.”
Among women in the United States, rates of ionizing radiation imaging were highest in women who were younger than 20 or older than 40, women who were black, Hispanic or American Indian, and women who gave birth preterm.
Among black women in the U.S., 1.49 percent of pregnancies underwent CT scans, along with 1.16 percent of American Indian pregnancies. Just 0.74 percent of white pregnancies underwent CT scans and only 0.46 percent of Asian pregnancies had the same examination.
“It is unclear why there are possible racial and age disparities in the receipt of medical imaging by pregnant women,” the study said. “We hypothesize that minority women and younger women, compared with their counterparts, might be seen more often in emergency settings for abdominal pain where imaging is performed for clinical workup.”
Miglioretti said the good news is that the trend seems to be stabilizing. Following a big leap from 1996 to 2007, CT scanning rates tapered off and even began to decline slightly in the U.S. between 2010 and 2016.
“I hope that we’ll see that the rates continue to come down,” Miglioretti said. “Also, the rates are much lower than in the general population — about 13 times lower than the general population — so it does seem like physicians and radiologists are trying to limit imaging of pregnant women, but there of course will always be situations where it’s medically necessary.”
Of the 3.4 million pregnancies included in the study, 26 percent were in the United States, 92 percent were in women age 20 to 39 and 85 percent of them resulted in full-term births.
Data points were drawn from health care sites in four Kaiser Permanente regions — Northern California, Northwest, Washington and Hawaii — plus the Marshfield Clinic Health System in Wisconsin, Harvard Pilgrim Health Care in Massachusetts and Ontario, Canada’s provincial health care system.
“Imaging can be helpful, but it can be overused,” Smith-Bindman said in a prepared statement. “Always, but especially if you’re pregnant, you should ask whether it is really medically necessary to have any imaging test that involves ionizing radiation.”