What are the risks of a sinus computed tomography (CT) scan on a pregnancy at 7 weeks gestation?

From the Guidelines

A sinus CT scan during early pregnancy, such as at 7 weeks gestation, poses minimal risk to the developing fetus, and if medically necessary, the benefit typically outweighs the minimal risk. The radiation dose from a standard sinus CT scan is approximately 0.2-0.6 millisieverts (mSv), which is well below the threshold of 50-100 mSv that has been associated with potential fetal harm 1. At 7 weeks gestation, the primary concern would be radiation exposure, but the focused nature of a sinus CT means that the radiation beam is directed at the head, far from the uterus, further reducing fetal exposure.

Key Considerations

• The developing embryo is most vulnerable to radiation effects during organogenesis (2-8 weeks), but the actual risk from this procedure is extremely low 1.
• Non-contrast CT is preferred when possible, as iodinated contrast agents cross the placenta, though no definitive adverse effects have been documented from contrast exposure.
• If the sinus CT is medically necessary for diagnosis or treatment planning, the benefit typically outweighs the minimal risk, as stated in the guidelines for the management of urgent obstetric situations in emergency medicine 1.
• Alternative imaging such as MRI might be considered if clinically appropriate, as it involves no ionizing radiation.
• Always inform your radiologist and technicians about your pregnancy so they can use appropriate shielding and optimize the scan parameters to minimize exposure.

Radiation Risk

The estimated increase of cancer incidence following fetal exposure to 50 mGy is 1.1 to 3 by 1000, which leads us to conclude that the risk of developing cancer subsequent to application of an imagery technique is minimal 1.

Clinical Decision

Any healthcare professional whose management of a pregnant woman requires imagery for diagnostic purposes is called upon to take into consideration the risk-benefit balance of exposure to radiological procedure 1.

From the Research

Risks of Sinus CT Scan on Pregnancy at 7 Weeks Gestation

• The risks of a sinus CT scan on a pregnancy at 7 weeks gestation include slow growth and development of the fetus, abortion, malformations, impaired brain function, abnormal childhood growth, and neurological development 2.
• Fetuses are more sensitive to radiation and the effects of medical imaging as compared to adults since they have a rapidly developing cell system 2.
• The scanning parameters that influence dose and the techniques for estimating and reducing dose are explained, and fetal radiation doses for CT examinations in which the fetus is not directly imaged, such as head or chest CT, are minimal and need not figure in the risk-benefit analysis to perform the examination 3.
• However, radiation dose should be considered with abdominopelvic CT because the fetus is likely to be exposed directly to the scanning beam 3.
• The accepted cumulative dose of ionizing radiation during pregnancy is 5 rad, and no single diagnostic study exceeds this maximum 4.
• The most sensitive time period for central nervous system teratogenesis is between 10 and 17 weeks of gestation, but since the pregnancy is at 7 weeks gestation, this is not a concern 4.
• Rare consequences of prenatal radiation exposure include a slight increase in the incidence of childhood leukemia and, possibly, a very small change in the frequency of genetic mutations 4.
• It is essential for pregnant women to discuss the benefits and risks of medical imaging with their physicians before undergoing any CT scan 2, 5.