From the Guidelines
CT scans should not be avoided in pregnant women when medically necessary, as the risk of cancer incidence following fetal exposure to radiation is minimal, with an estimated increase of 1.1 to 3 per 1000 1. The primary concern with performing CT scans on pregnant women is the potential risk of childhood cancer due to ionizing radiation. However, the absolute risk remains small, with an overall risk of death by cancer during childhood being extremely low (1 to 2.5 per 1000) 1. Some key points to consider include:
- The risk of cancer incidence following fetal exposure to radiation is minimal, with an estimated increase of 1.1 to 3 per 1000 1.
- Fetal radiation doses above 50 mGy are associated with a doubled relative risk of death by cancer during childhood 1.
- Most diagnostic CT scans deliver less than 50 mGy to the fetus, which falls below the threshold of 100 mGy associated with congenital malformations or intellectual disability.
- Alternative imaging methods like ultrasound or MRI, which don't use ionizing radiation, should be considered first when clinically suitable.
- When CT is deemed necessary, techniques to minimize radiation exposure should be employed, including using the lowest dose possible, limiting the scan area, and using lead shielding when appropriate 1. It's also worth noting that the gestational age is important, with the first trimester being the period of highest radiosensitivity for organ malformations, though cancer risk exists throughout pregnancy 1. In terms of statistics, the estimated increase in cancer incidence following fetal exposure to 50 mGy is 1.1 to 3 per 1000, which leads to the conclusion that the risk of developing cancer subsequent to application of an imaging technique is minimal 1. Overall, the benefits of CT scans in pregnant women outweigh the risks when medically necessary, and they should not be avoided due to pregnancy 1.
From the Research
Risks Associated with CT Scans on Pregnant Women
- Exposure to a single abdominal CT does not appear to increase the risk of spontaneous abortion or congenital malformations, but it is thought to double the risk of childhood cancer 2
- The risk of radiation exposure to the fetus is increased, so more than the usual benefit is necessary to justify computed tomography (CT) than in non-pregnant patients 3
- Fetal radiation doses up to 1 mGy are considered acceptable; with larger doses, the risk of carcinogenesis approximately doubles, although it remains low in absolute terms 4
- Although teratogenesis is not a major concern after exposure to prenatal diagnostic radiation, carcinogenesis is a potential risk 5
Statistics and Guidelines
- The use of computed tomography (CT) and magnetic resonance (MR) imaging has increased tremendously in the past 2 decades, making it more likely for pregnant and breast-feeding women to require contrast material-enhanced imaging 4
- Ultrasonography is the initial modality of choice for suspected appendicitis, but if the ultrasound examination is negative, MRI or CT can be obtained 5
- CT should be the initial diagnostic imaging modality for suspected pulmonary embolism 5
- Ultrasonography should be the initial study of choice for suspected renal colic 5
- Low-dose CT pelvimetry can be performed with minimal risk for suspected cephalopelvic disproportion 5
Contrast Agents and Radiation
- The use of iodinated contrast agents is generally safe during pregnancy, but should be used with caution due to the risk of fetal hypothyroidism 4
- The use of gadolinium-based contrast agents during pregnancy remains controversial due to lack of human clinical data and potential toxicity 4
- Radionuclide procedures are reluctantly ordered by clinicians in pregnant patients, because of the malpractice fear or because of uncertainty regarding fetal radiation dose, but when used appropriately, the benefits of nuclear imaging procedures usually outweigh the minimal risks associated with small amount of radiation even in pregnant patients 6