From the Guidelines
Yes, a CT angiogram in a 24-week pregnant patient exposes the fetus to both contrast and radiation. The iodinated contrast agent used in CT angiography crosses the placenta and enters the fetal circulation, though no definitive teratogenic effects have been documented 1. The radiation dose from a CT angiogram typically ranges from 5-15 mSv depending on the protocol and area scanned, with the fetus receiving a fraction of this dose, as seen in Table 3 of the study by 1, which lists the fetal dose for a CT abdomen/pelvis as 13-25 mGy. While this level of radiation is below the 50 mSv threshold considered potentially harmful to fetal development, the principle of ALARA (As Low As Reasonably Achievable) should be applied 1. Some key points to consider include:
- Alternative imaging modalities like MRI or ultrasound should be considered first when possible, as they don't use ionizing radiation 1.
- If CT angiography is medically necessary and the diagnostic information cannot be obtained through other means, the benefit to the mother's health may outweigh the theoretical risk to the fetus 1.
- The radiologist should optimize the CT protocol to minimize radiation exposure while maintaining diagnostic quality, and the patient should be informed about the risks and benefits before proceeding with the examination 1.
- Iodinated contrast can potentially cause neonatal hypothyroidism, but most CT studies now use non-ionic contrast, which has no effect on the thyroid gland 1.
- The use of iodinated contrast is recommended only if essential, and breastfeeding after iodinated contrast is considered safe 1.
From the Research
CT Angiogram in Pregnancy
- A CT angiogram in a 24-week pregnant patient does expose the fetus to radiation 2, 3.
- The use of iodinated contrast agents, commonly used in CT scans, has not been well studied in human subjects during pregnancy 2.
- However, it is known that contrast agents can pose risks to the fetus, and their use should be carefully considered 4, 5.
- Alternative imaging modalities, such as ultrasound or MRI, may be preferred to minimize radiation exposure to the fetus 3, 6.
- The decision to use a CT angiogram with contrast in a pregnant patient should be made on a case-by-case basis, weighing the potential benefits against the potential risks to the fetus 2, 5.
Radiation Exposure
- Radiation exposure from a CT angiogram can be affected by gestational age, anatomic site, modality, and technique 2.
- The risks associated with radiation exposure to the fetus should be carefully considered and discussed with the patient 2, 5.
Contrast Agents
- Iodinated contrast agents are commonly used in CT scans, but their use during pregnancy has not been well studied 2.
- Microbubble contrast agents used in contrast-enhanced ultrasound do not cross the placental barrier and have been shown to pose no harm to the fetus in animal studies 3.
- Gadolinium-based contrast agents used in MRI may be associated with a slightly higher rate of neonatal death, although more research is needed to confirm this finding 6.