Preconception CT linked to miscarriage and birth defect risks

Preconception CT linked to miscarriage and birth defect risks | Image Credit: © Gorodenkoff - © Gorodenkoff - stock.adobe.com.

A study published in the Annals of Internal Medicine has reported associations between exposure to preconception computed tomography (CT) imaging with spontaneous pregnancy loss and congenital anomalies.¹

While CT imaging is vital for disease diagnosis and surveillance, it has been linked to increased ionizing radiation exposure, and use has significantly risen in the past 3 decades. The ovarian follicle has prolonged dormancy and a gradual maturation process, making it potentially more vulnerable.²

“Much less is known about pregnancy viability or the risk for a congenital anomaly if exposure to CT ionizing radiation occurs well before conception,” wrote investigators.¹

CT exposure analysis

The population-based cohort study was conducted to evaluate the impact of CT ionizing radiation exposure before conception on spontaneous pregnancy loss and congenital or chromosomal anomaly risks. Data was obtained from databases in the Ontario province.

Pregnant women aged 16 to 45 years between April 1, 1992, and March 31, 2023, were included in the analysis. Hospital-based live births were separately identified to determine congenital or chromosomal abnormalities, and only first-born children were included for multifetal pregnancies.

Exclusion criteria included non-Ontario residence, prothrombotic risk factors, CT imaging during pregnancy, and not having an Ontario Health Insurance Plan number. The cumulative number of CT scans completed up to 4 weeks before conception was reported as the exposure, including 0, 1, 2, and 3 or more.

The cumulative number of CT scans limited to the pelvic, abdomen, sacral spine, or lumber spine were reported as secondary exposures. Spontaneous pregnancy loss, including miscarriage, ectopic pregnancy before 20-weeks’ gestation, or stillbirth at 20-weeks’ gestation or later was the primary outcome. Congenital and chromosomal anomalies were also reported.

Study population profile

There were 5,142,339 women included in the final analysis,13.4% of whom received a CT scan at a median 50 months between the most recent scan and conception. Participants were aged a mean 29 years at pregnancy, and 10% lived in a rural region at the index pregnancy.

Of patients with a CT scan, diabetes mellitus and chronic hypertension were reported in 2.2% and 3.7%, respectively. In comparison, these rates were 1.4% and 1.6%, respectively, among those without a CT scan. CT-exposed patients also had higher rates of sexually transmitted infections, obesity, pelvic inflammatory disease, endometriosis, smoking, and thyroid disorders.

Spontaneous pregnancy loss was reported in 10.4% of pregnancies, with 9.1% being miscarriage, 0.92% ectopic pregnancy, and 0.39% stillbirth. Rates of pregnancy loss were 101, 117, 130, and 142 per 1000 pregnancies in patients with 0, 1, 2, and 3 or more prior CT scans, respectively.

These values indicated adjusted hazard ratios (aHRs) of 1.08, 1.14, and 1.19 for 1, 2, and 3 or more CT scans, respectively, vs no prior scans. Slight increases in absolute rates were also observed when limiting CT imaging to the pelvic, abdomen, or lower spine, while a slight decrease was observed when limiting CT imaging to the head.

Congenital anomalies and CT exposure

Findings did not significantly change when shifting the end time for CT exposure to 2 weeks before the estimated date of conception. When the timing of the most recent CT scan was 4 to 8 weeks before conception, the aHR was 1.24.

An increase in the rate of congenital anomalies was also reported in patients with CT scans, at 61, 84, 96, and 105 per 1000 live births for 0, 1, 2, and 3 or more scans. These indicated aHRs of 1.06, 1.11, and 1.15 for 1, 2, and 3 or more scans, respectively, vs no prior scans. Overall, the results highlighted increased odds of miscarriage and congenital anomalies from CT scans.

“In young women, alternative imaging methods to CT should be considered, when appropriate,” wrote investigators.

References

1. Simard C, Fu L, Odugbemi T, et al. Exposure to computed tomography before pregnancy and risk for pregnancy loss and congenital anomalies: A population-based cohort study. Annals of Internal Medicine. 2025. doi:10.7326/ANNALS-24-03479
2. Zondervan RL, Hahn PF, Sadow CA, et al. Frequent body CT scanning of young adults: indications, outcomes, and risk for radiation-induced cancer. J Am Coll Radiol. 2011;8:501-507. doi:10.1016/j.jacr.2010.12.025