A large Canadian study has found that women exposed to radiation from CT scans shortly before becoming pregnant may face higher risks of miscarriage and birth defects in their babies.
The findings, published in the Annals of Internal Medicine, suggest that doctors should carefully consider alternative imaging methods for women of reproductive age whenever possible.
CT scans, or computed tomography scans, are commonly used to diagnose medical problems because they provide detailed images of the body.
However, they use ionizing radiation, which has long been known to damage DNA and potentially harm developing embryos and fetuses.
Until now, little research had examined whether exposure to CT scans before conception could affect future pregnancies.
Researchers from the Jewish General Hospital in Montreal, along with colleagues in Ontario, studied data from more than 5.1 million pregnancies and 3.4 million live births between 1992 and 2023. The women in the study were aged 16 to 45.
Out of all the pregnancies examined, nearly 688,000 women had undergone a CT scan before conception.
Overall, about 10% of recognized pregnancies ended in spontaneous pregnancy loss, which included miscarriages, ectopic pregnancies, and stillbirths.
But the risk was higher among women who had CT scans prior to conceiving. For women with no prior CT scan, there were about 101 pregnancy losses per 1,000 pregnancies. That rate rose to 117 per 1,000 after one CT scan, 130 per 1,000 after two scans, and 142 per 1,000 after three or more scans.
The risk was even greater when the CT scans involved the abdomen, pelvis, or lower spine—areas closer to reproductive organs. The study also found that the closer in time a CT scan occurred to conception, the greater the risk of pregnancy loss.
The researchers also looked at congenital anomalies, or birth defects, diagnosed within the first year of life.
Among women with no CT scan before conception, there were 62 anomalies per 1,000 live births. That number increased to 84 per 1,000 after one CT scan, 96 per 1,000 after two scans, and 105 per 1,000 after three or more scans.
While the absolute risks remain relatively low, the study highlights a clear pattern: the more CT scans a woman had before conception, and the closer those scans were to the time of conception, the higher the risks of miscarriage or birth defects.
The authors stress that CT scans are often essential and lifesaving, but when it comes to younger women who may become pregnant, physicians should carefully weigh the risks and consider safer alternatives such as ultrasound or MRI when appropriate.
These findings could help shape future guidelines on imaging practices for women of childbearing age, aiming to balance the benefits of CT scans with the need to protect reproductive health.
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