Research published in the Annals of Internal Medicine regarding the use of CT before pregnancy overstates the modality’s potentially negative effects, according to the American Association of Physicists in Medicine (AAPM).
A study conducted by a team of Canadian investigators and posted September 9 in the Annals concluded that “exposure to preconception CT imaging may be associated with higher risks for spontaneous pregnancy loss and congenital anomalies … [and that] alternative imaging methods should be considered when appropriate.”
The research included data from 5.1 million recognized pregnancies and 3.4 million live births from between 1992 and 2023; pregnant women were exposed to CT imaging up to four weeks before conception. Comorbidities such as diabetes, hypertension, obesity, and smoking were more common in those exposed to CT imaging, wrote a team led by Camille Simard, MD, of Lady Davis Institute for Medical Research in Montreal. The group reported the following:
|
Effect of preconception CT scans on ensuing pregnancies |
||||
|
Outcome |
Zero CT scans |
One CT scan |
Two CT scans |
Three or more CT scans |
| Spontaneous pregnancy loss (per 1,000 pregnancies) |
101 |
117 (hazard ratio, or HR, with 1 as reference: 1.08) |
130 (HR: 1.14) |
142 (HR: 1.19) |
| Rates of congenital abnormalities (per 1,000 live births) |
62 |
84 (HR: 1.06) |
96 (HR: 1.11) |
105 (HR: 1.15) |
“The risk observed with head CT was not consistently lower than with CT of the abdomen, pelvis, or lower spine,” Simard and colleagues wrote.
But in two statements released September 18, the AAPM sought to put the research and an accompanying editorial into perspective, noting that “comorbidities, and not radiation dose, likely explain study results.”
“In this study, the authors conclude that exposure to CT imaging before conception was associated with a modestly elevated risk for miscarriage and congenital anomalies,” the AAPM wrote. “However, they found this to be true both for exposures to the abdomen or pelvis and for exposures to the head only, which they rightly consider to be their negative control (the dose to the ovaries from a head CT exam is essentially zero). If head CT exams, with no ovary exposure, resulted in an increase in miscarriage and congenital anomalies, radiation dose to the ovaries does not explain their findings.”
The Association noted that “the women who had CT exams had higher comorbid conditions in the two years before conception, including obesity, diabetes mellitus, sexually transmitted infection, pelvic inflammatory disease, endometriosis, thyroid disorder, mental health condition, and smoking. The observed rates of these comorbidities were approximately 50 to 100% higher in the women who received CT exams. These data support that individuals receiving a CT exam have some pre-existing medical condition that warrant advanced medical imaging. Hence, the reason for the CT exam (of the head or abdomen/pelvis) better explains the observed outcomes, rather than the CT exam (and radiation) itself.”
The AAPM also critiqued the editorial regarding the study, writing that it “dismisses the extensive research on this topic over the past nine decades, which has been so extensively studied precisely because radiologists, clinicians, health and medical physicists, regulators, epidemiologists, and teratologists all care intensely about ensuring that exposure to ionizing radiation from medical procedures is safe for the present or future conceptus of the irradiated patient.”
While the Simard study results “should not be dismissed, the results should not be considered ‘profound,'” – and will not change the AAPM’s recommendations, it said.
“The study’s results do not sufficiently support the claim that having more than one to three CT scans prior to pregnancy affects fetal outcomes,” it concluded.
The complete Annals study can be found here.