Can You Have a CT Scan While Pregnant?

Can You Have a CT Scan While Pregnant?

Short answer: Yes, when the scan is medically necessary. The American College of Obstetricians and Gynecologists (ACOG) and the American College of Radiology (ACR) state that a needed CT should not be withheld from a pregnant patient. A single diagnostic CT delivers a fetal dose well below 50 mGy, the level under which no increase in birth defects or pregnancy loss has been shown. Radiation-free options — ultrasound or MRI — are used first whenever they can answer the clinical question.

If you are pregnant and a doctor has mentioned a CT scan, the worry is understandable. CT uses X-rays, and everyone has heard that radiation and pregnancy do not mix. The real picture is more reassuring than that, and it comes down to numbers. Here is how radiologists at Advanced Medical Imaging in Seminole, FL think through the decision.

The Number That Matters: 50 mGy

Fetal radiation risk is measured in milligray (mGy). Decades of data — including studies of atomic-bomb survivors and medically exposed patients — have established that the threshold for deterministic effects (miscarriage, growth restriction, malformations, intellectual disability) is approximately 50 mGy to the fetus, and in most analyses closer to 100 mGy.

How do common CT exams compare?

• Head CT: less than 0.005 mGy to the fetus (essentially zero — the fetus is outside the beam)
• Chest CT / CT pulmonary angiogram: roughly 0.01–0.66 mGy
• Abdominal CT: roughly 1.3–35 mGy
• Abdomen and pelvis CT: roughly 10–50 mGy
• Pelvic CT: roughly 10–50 mGy

Every exam outside the abdomen and pelvis exposes the fetus to a small fraction of one mGy. Even a full abdominopelvic CT, performed once, sits at or below the threshold, and modern dose-reduction protocols routinely bring it lower. For context, a fetus receives about 1 mGy of natural background radiation across a normal pregnancy.

What the Guidelines Say

ACOG Committee Opinion 723, Guidelines for Diagnostic Imaging During Pregnancy and Lactation, states that exposure to radiation from a single diagnostic procedure does not result in harmful fetal effects and that CT "should not be withheld from a pregnant patient" when it is the appropriate test. The ACR–SPR Practice Parameter on imaging pregnant patients reaches the same conclusion and emphasizes using the lowest dose that answers the question.

The guiding principle is straightforward: an undiagnosed condition in the mother is usually the larger risk to the pregnancy. A missed pulmonary embolism, ruptured appendix, or kidney obstruction endangers both patient and fetus far more than a well-planned CT.

When CT Is Used During Pregnancy

Ultrasound is always the first tool, and MRI is the usual second step for non-emergent questions. CT is chosen when speed and accuracy matter most:

• Suspected pulmonary embolism — CT pulmonary angiography (see our PE CT guide); fetal dose is negligible because the pelvis is outside the scan range
• Major trauma — motor-vehicle collisions and falls where minutes count
• Suspected appendicitis when ultrasound is inconclusive and MRI is not immediately available
• Kidney stones with complications, after ultrasound
• Severe headache or neurological change requiring urgent head imaging
• Cancer staging when a treatment decision cannot wait

How the Dose Is Kept Low

When a pregnant patient does need CT, several steps reduce the fetal dose further:

• Limiting the scan range to only the region required
• Automatic dose modulation that adjusts output to body size
• Iterative reconstruction software that produces diagnostic images at lower exposure (read about how modern CT reduces radiation)
• Single-phase imaging — avoiding repeated passes through the same area
• Avoiding unnecessary repeat scans by making sure the first exam is done correctly

Lead shielding over the abdomen was standard for years; current ACR and AAPM guidance no longer recommends it for CT, because it does not reduce the internal scatter that produces most of the fetal dose and can interfere with automatic exposure control. Do not be alarmed if a shield is not used — that reflects the newest evidence, not carelessness.

What About Iodinated Contrast?

CT contrast (iodine-based) crosses the placenta. Human studies have not shown teratogenic effects, and ACOG considers it acceptable when it is needed for diagnosis. The theoretical concern is a temporary effect on the fetal thyroid, so newborns exposed in utero are typically checked with the standard newborn thyroid screen — which every baby in Florida receives anyway. As with any contrast, we confirm kidney function and allergy history first. See our CT contrast preparation guide for the general checklist.

Breastfeeding does not need to be interrupted after iodinated contrast; less than 1% of the dose reaches breast milk and almost none is absorbed by the infant.

"I Had a CT Before I Knew I Was Pregnant"

This is one of the most common calls we receive. In almost every case the answer is reassuring: a single CT performed early in pregnancy, even of the abdomen, falls below the harm threshold. ACOG explicitly states that a diagnostic exam below 50 mGy is not a reason to consider ending a pregnancy. Tell your OB so the exposure can be documented; if you want an exact figure, the imaging facility can calculate a fetal dose estimate from the scan parameters.

When to Choose MRI or Ultrasound Instead

If a CT is being considered for a non-emergency reason, ask whether a radiation-free exam can answer the same question. At AMI:

• Ultrasound is first-line for pelvic pain, gallbladder, kidney, and fetal evaluation
• Open MRI and 3T MRI handle appendicitis, spine, brain, and most abdominal questions without radiation — read Is MRI Safe During Pregnancy?
• CT is reserved for the situations above where it is clearly the better test

Our radiologists review every request from a pregnant patient before it is scheduled, and self-pay patients can request imaging without an outside referral. Pricing is published up front — see self-pay pricing.

What to Tell Us When You Schedule

1. That you are pregnant or may be, and how many weeks along.
2. What symptom or question the scan is meant to answer — this lets the radiologist decide whether ultrasound or MRI can do the job instead.
3. Any prior imaging for the same problem, so nothing is repeated unnecessarily.

The Bottom Line

A necessary CT scan during pregnancy is safe by every major medical standard, and the risk of skipping a needed diagnosis is almost always greater than the risk of the scan. When the question can be answered without radiation, we use ultrasound or MRI. When it cannot, CT is performed with the lowest dose that gives your doctor a clear answer. Schedule online or call (727) 398-5999 and let us know you are pregnant — we will plan the exam around it.

Sources: - ACOG Committee Opinion No. 723 — Guidelines for Diagnostic Imaging During Pregnancy and Lactation - ACR–SPR Practice Parameter for Imaging Pregnant or Potentially Pregnant Patients with Ionizing Radiation - AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding (2019)