Preconception CT Scans Tied to Higher Risk of Pregnancy Loss, Congenital Anomalies: Daily Dose

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On September 10, 2025, we reported on a study published in Annals of Internal Medicine that was designed to examine the risk for spontaneous pregnancy loss and congenital anomalies in offspring of women exposed to computed tomography (CT) ionizing radiation before conception.

The study

Investigators analyzed 5 142 339 recognized pregnancies and 3 451 968 live births in Ontario between 1992 and 2023 among women aged 16 to 45 years. Among these pregnancies, 687 692 involved women who had undergone at least 1 CT scan at least 1 month before conceiving. The exposure was the cumulative number of CT scans up to 4 weeks before conception. Primary outcomes of interest were spontaneous pregnancy loss (miscarriage, ectopic pregnancy, or stillbirth) among recognized pregnancies and congenital anomalies diagnosed within the first year of life among live births.

The findings

Rates of spontaneous pregnancy loss, including miscarriage, ectopic pregnancy, and stillbirth, were 101 per 1000 pregnancies among those with no prior CT scans, compared with 117, 130, and 142 per 1000 among those with 1, 2, and 3 or more scans, respectively.

After adjusting for individual risk factors, researchers observed the odds of pregnancy loss were 8% higher (aHR 1.08; 95% CI, 1.07–1.08) for 1 scan, 14% higher (1.14, 1.12–1.16) for 2, and 19% higher (1.19, 1.16–1.21) for 3 or more scans.

Among live births, rates of congenital anomalies were 62 per 1,000 births in those with no previous CT scans, compared with 84, 96, and 105 per 1000 for mothers with 1, 2, and 3 or more scans, respectively, for an adjusted increased risk of 6% (CI, 1.05–1.08), 11% (CI, 1.09–1.14), and 15% (CI, 1.11–1.18) for 1, 2 and 3 or more scans.

Authors' comments

"Exposure to preconception CT imaging may be associated with higher risks for spontaneous pregnancy loss and congenital anomalies, but causal mechanisms remain to be elucidated. Alternative imaging methods should be considered when appropriate."

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