Exposure to CT scan may raise risks for pregnancy loss, congenital anomalies

Exposure to computed tomography (CT) imaging prior to pregnancy appears to increase the risks for spontaneous pregnancy loss and congenital anomalies, suggests a study. However, the mechanism driving this association remains unclear.

This population-based observational study included a total of 5,142,339 pregnancies and 3,451,968 live births between 1992 and 2023 in Ontario, Canada.

The cumulative number of CT scans up to 4 weeks before conception was the main exposure, while outcomes included spontaneous pregnancy loss (miscarriage, ectopic pregnancy, or stillbirth) among pregnancies and congenital anomalies diagnosed within the first year of life among live births.

The mean maternal age was 29 years. Women exposed to CT imaging were more likely to present with diabetes, hypertension, obesity, and be smokers.

Among recognized pregnancies, the spontaneous pregnancy loss rates were 101, 117, 130, and 142 per 1,000 pregnancies with zero, one (adjusted hazard ratio [aHR], 1.08, 95 percent confidence interval [CI], 1.07–1.08), two (aHR, 1.14, 95 percent CI, 1.12–1.16), and three or more preconception CT scans (aHR, 1.19, 95 percent CI, 1.16–1.21), respectively.

Moreover, the congenital anomaly rates among live births were 62, 84, 96, and 105 per 1,000 births in those with zero, one (aHR, 1.06, 95 percent CI, 1.05–1.08), two (aHR, 1.11, 95 percent CI, 1.09–1.14), and three or more CT scans (aHR, 1.15, 95 percent CI, 1.11–1.18).

“The risk observed with head CT was not consistently lower than with CT of the abdomen, pelvis, or lower spine,” the authors said. 

“Alternative imaging methods should be considered when appropriate,” they added.