CT Scan When Pregnant: Safety, Benefits, And Risks

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A computerized tomography (CT) scan, also referred to as computed axial tomography (CAT), is a non-invasive imaging technique. It uses specialized X-rays to produce cross-sectional images of the structures inside the body. CT scan while pregnant is recommended only in emergencies since there is a considerable chance the X-rays might harm the fetus (1) (2).

CT scan is useful for diagnostic purposes and checking internal organs, including blood vessels, bones, and organs. Read on to understand the safety, risks, and alternatives of CT scan in pregnancy.

Is It Safe to Perform CT Scan During Pregnancy?

CT scans are usually not recommended during any trimester of pregnancy unless a life-saving decision for the mother depends on it. However, the American College of Radiology states that a single diagnostic X-ray does not have a significant radiation dose to cause adverse effects in a developing fetus. Nevertheless, it is important to inform your healthcare provider about your pregnancy before undergoing CT scans or any medical procedures (3).

Why Are CT Scans Performed?

CT scans produce images without the insertion of any equipment inside the body or surgical procedure. It may be conducted for the following purposes (2).

  • Diagnose certain conditions such as damage to bones, internal organ injuries, problems with blood flow, stroke, and cancer.
  • Guide further tests or treatments, such as determining tumor location, shape, and size before radiotherapy.
  • Locate areas before taking a needle biopsy sample or drain an abscess.
  • Monitor conditions, including checking an anomaly, during and after treatment.

Why Do You Need A CT Scan During Pregnancy?

A CT scan for medical imaging may be advised by your doctor if you have symptoms that need screening for detection but cannot wait until childbirth. These may include the following conditions (3) (4).

  • Acute appendicitis or obstruction in the small bowel
  • Blood clots in the head
  • Abnormalities or infections in the heart and lungs
  • Bone fractures or herniated intervertebral disks (slipped disk)

What Are The Risks Of A CT Scan During Pregnancy?

A fetus is considered more sensitive to the adverse effects of ionizing radiation found in X-rays and CT scans. Organs develop between two and 15 weeks of pregnancy (organogenesis phase), and the fetus is most susceptible to the harmful effects of ionizing radiation during this period (5).

The safe threshold limit of the absorbed dose of radiation from a CT scan for a fetus is 100mGy (milligray) (6). However, most CT scans may not cross more than 50mGy. More scans lead to more exposure to ionizing radiation, increasing the risk of fetal health conditions.

The in-utero exposure to higher doses of radiation may lead to the following problems (5).

  • Microcephaly (abnormally small head)
  • Microphthalmia (eye malformation)
  • Mental retardation
  • Growth retardation
  • Behavioral defects
  • Cataracts clo
  • Childhood cancers

Scans that do not directly expose the fetus to radiation cause very little exposure. These include CT scans of areas such as the head (including dental scans), neck (cervical and thoracic spine), chest, and extremities (knees, legs, shoulders).

A significant exposure occurs only when the fetus is within the primary beam. This may happen during a CT scan of the pelvic region, and doses vary from 10-50mGy, depending on the gestational age and scanning parameters (7).

The table below may help you understand the extent of fetal radiation exposure due to CT scans of different body areas (4).

CT scan regionEstimated fetal dose per examination (mGy)
Head0.001-0.01
Chest0.01-0.66
Abdomen1.3-35
Pelvis10-50

Some CT scans require an intravenous injection or oral administration of contrast material for better imaging. Oral contrast materials may cross the placenta, but no adverse effects have been reported. A contrast material could improve the images generated, leading to a better diagnosis. This could reduce the need for further scans, reducing fetal exposure to more radiation.

What Are The Alternatives To A CT Scan?

Ultrasonography (USG) and magnetic resonance imaging (MRI) are preferred techniques over a CT scan during pregnancy. These methods do not use ionizing radiation and are less risky to the unborn child. However, even these should be used only when clinically relevant or beneficial to the pregnant patient (4).

Techniques involving ionizing radiation, such as CT or CAT scans, should be used only when necessary during pregnancy. The ultimate goal of the radiologist is to minimize the fetal radiation dose. Discuss the potential risk and benefit of the procedure if you are advised an abdominal or pelvic CT. Inform the CT technologist and the radiologist about your pregnancy so that they may adjust the procedure to lower the radiation dose.

Key Pointers

  • Computerized tomography (CT) scans are generally not advised during pregnancy except in case of serious symptoms, such as heart or lung abnormalities, which require immediate attention.
  • The ionizing radiation from CT scans may interfere with organogenesis and cause fetal health complications.
  • Ultrasonography (USG) and magnetic resonance imaging (MRI) are preferable over CT scans during pregnancy.

References:

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Dr. Annal Vaidya

(MS)
Dr. Annal Vaidya is a former assistant professor of Obstetrics and Gynecology at the prestigious Seth GS Medical College and KEM Hospital, Mumbai. He currently works as a consultant in various hospitals in the city. Dr. Vaidya specializes in managing high-risk pregnancies, infertility, and complicated pregnancies. He has a special interest in Cosmetic Gynecology and Endoscopy.

Dr. Joyani Das

Dr. Joyani Das is a PhD in Pharmacology with over two years of experience in academics. Previously, she worked as an associate professor, faculty of Pharmacology. With her research background in preclinical studies and a zeal for scientific writing, she joined MomJunction as a health writer. Her research work was published in international journals and publications, such as Elsevier, Current... more