Is Computed Tomography Angiography (CTA) of the chest safe during pregnancy?

From the Guidelines

CT angiography (CTA) of the chest can be performed safely during pregnancy when medically necessary, but it should be used judiciously. The primary concern is radiation exposure to the fetus, which is approximately 0.01-0.66 mGy for a chest CTA, well below the threshold of 50 mGy that might cause fetal harm, as stated in the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1. The contrast agent (iodinated contrast) used in CTA crosses the placenta but has not been shown to cause harm to the developing fetus. However, alternative imaging methods that don't use radiation, such as ventilation-perfusion (V/Q) scanning or MRI without gadolinium, should be considered first when evaluating for pulmonary embolism, which is a common indication for chest CTA in pregnancy. If CTA is deemed necessary, radiation dose should be minimized using techniques like dose modulation and limiting the scan range. The benefit of accurate diagnosis of potentially life-threatening conditions like pulmonary embolism, aortic dissection, or severe pneumonia typically outweighs the small theoretical risk to the fetus. The mother should be informed about the risks and benefits, and a lead shield should be placed over the abdomen during the procedure, though this provides mainly psychological reassurance as modern CT scanners limit scatter radiation effectively.

Some key points to consider:

• The estimated increase of cancer incidence following foetal 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, as stated in the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1.
• Ultrasound and magnetic resonance imaging are the usual imaging techniques recommended for pregnant women, but if thoracic, abdominal and pelvic computed tomography (TAP CT) is necessary and more rapidly accessible and appropriate for diagnostic and/or therapeutic management, it should not be avoided due to the patient’s pregnancy, as stated in the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1.
• 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, as stated in the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1.

In terms of the most recent and highest quality study, the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1 provide the most up-to-date and relevant information on this topic. This study provides a comprehensive overview of the risks and benefits associated with CTA during pregnancy and emphasizes the importance of judicious use of this imaging modality. The study also highlights the need for alternative imaging methods and the importance of minimizing radiation dose when CTA is deemed necessary. Overall, the guidelines for the management of urgent obstetric situations in emergency medicine, 2022 1 provide a clear and evidence-based approach to the use of CTA during pregnancy.

From the Research

Computed Tomography Angiography (CTA) of the Chest During Pregnancy

• The safety of Computed Tomography Angiography (CTA) of the chest during pregnancy is a concern due to the potential risks of radiation exposure to the fetus 2, 3.
• Studies have shown that the fetal dose from CT scans of the maternal chest can be reduced by using strategies such as mA modulation, shielding with a lead coat, and shorter scan lengths 4, 5.
• The estimated fetal doses from CT pulmonary angiography (CTPA) in late pregnancy have been reported to be in the range of 60-230 microGy 5.
• Guidelines for the use of CT and MRI during pregnancy and lactation recommend that CT should be the initial diagnostic imaging modality for suspected pulmonary embolism, and that ultrasonography should be the initial study of choice for suspected renal colic or appendicitis 6.
• It is essential to weigh the benefits and risks of medical imaging during pregnancy and to discuss these with patients, as the risks of radiation exposure to the fetus must be balanced against the need for accurate diagnosis and treatment 2, 6.

Fetal Radiation Dose and Safety Measures

• The fetal radiation dose from CTPA can be reduced by shortening the scan length, which can lower the mean fetal absorbed dose by 70% 4.
• Shielding may increase the effective dose to the patient and the mean absorbed dose to the fetus, and may compromise automatic exposure control 4.
• The use of lead coats and shorter scan lengths can reduce the fetal radiation dose, but the effectiveness of these measures depends on the specific scanning protocol and equipment used 5.
• It is crucial to follow guidelines and recommendations for the safe use of CT and MRI during pregnancy, including the use of alternative modalities such as ultrasonography when possible 3, 6.