CT scans and pregnancy outcomes – new concerns

Review by Prof. Eamonn Quigley (USA)

Study Summary 

While this may be peculiar to the United States and a reflection of the overuse of expensive resources in our health care system, it has become virtually automatic for everyone who visits the emergency department (ED) with a GI problem to get a computed tomography (CT) scan. For those with chronic GI conditions like inflammatory bowel disease (IBD), scans are often repeated on multiple occasions. While we have been aware of the potential harm of radiation exposure to the fetus for decades and every x-ray department takes steps to avoid such exposure, this study examined the impact of CT scans before conception on pregnancy outcomes.¹ Using population-based data from the province of Ontario in Canada between 1992 and 2023, they examined the impact of exposure to CT scans up to 4 weeks before conception. In a retrospective study of over 5 million pregnancies among women aged 16 to 45, they analyzed the impact of pre-conception scanning on spontaneous pregnancy loss and congenital anomalies detected in infants during the first year of life. They detected a dose-dependent increase in rate for both outcomes among those who had CT scans, with the adjusted hazard ratio for pregnancy loss being 1.19 for those who had 3 or more scans, and the rate of congenital abnormalities rising from 62 to 105 per 1000 live births for those who had 0 and more than 3 scans, respectively. The closer the CT scanning was to the date of conception, the higher the rate of spontaneous pregnancy loss.

Commentary 

While the increases in absolute and relative risks for both spontaneous loss of pregnancy and congenital anomalies in infants were small, they were not insignificant and should, as emphasized in an accompanying editorial,² prompt all of us to think again when, as a reflex, we order a CT scan on a female of child-bearing potential who presents to the ED for some other GI problem. The increasing use of intestinal ultrasound in the assessment of IBD should also help to reduce CT utilization in this patient group. The mechanisms of these effects are not known but are suggested to be related to the effects of ionizing radiation on the ovarian follicle leading to DNA damage and, potentially, genetic mutations and chromosomal changes in the unfertilized oocyte.   

Citation

1. Simard C, Fu L, Odugbemi T, Simpson AN, Guan J, Tagalakis V, Delluc A, Ray JG. Exposure to computed tomography before pregnancy and risk for pregnancy loss and congenital anomalies. Ann Intern Med 2025;178:1539-48.
2. Hardy SM. Computed tomography exposure and risk for adverse outcomes in future pregnancies. Ann Intern Med 2025;178:1655-6.

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