Ann Intern Med

CT scans before pregnancy may increase risk of fetal harm

September 11, 2025

Preconception CT imaging may be associated with modestly increased risks of pregnancy loss and congenital anomalies. While causality is not established, these findings support consideration of alternative imaging modalities in reproductive-age women when clinically appropriate.

Study details: This large population-based cohort study in Ontario, Canada, included over 5 million recognized pregnancies and 3.4 million live births from 1992 to 2023. The exposure was the cumulative number of CT scans performed up to 4 weeks before conception. Outcomes assessed were spontaneous pregnancy loss (miscarriage, ectopic pregnancy, or stillbirth) and congenital anomalies diagnosed within the first year of life among live births.

Results: Rates of spontaneous pregnancy loss increased with the number of preconception CT scans: 101, 117, 130, and 142 per 1,000 pregnancies for 0, 1, 2, and ≥3 scans, respectively. Adjusted hazard ratios (aHRs) were 1.08 (95% confidence interval [CI], 1.07–1.08) for 1 scan, 1.14 (1.12–1.16) for 2, and 1.19 (1.16–1.21) for ≥3 scans. Congenital anomaly rates also rose with CT exposure: 62, 84, 96, and 105 per 1,000 births, with aHRs of 1.06 (1.05–1.08), 1.11 (1.09–1.14), and 1.15 (1.11–1.18) for 1, 2, and ≥3 scans, respectively. Risks weren't consistently lower for head CT compared with abdominal/pelvic/lower spine CT.

Source:

Simard C, et al. (2025, September 9). Ann Intern Med. Exposure to Computed Tomography Before Pregnancy and Risk for Pregnancy Loss and Congenital Anomalies : A Population-Based Cohort Study. https://pubmed.ncbi.nlm.nih.gov/40921077/