Quick answer: A CT scan during pregnancy is usually safe for the baby when it’s medically needed. According to the American College of Obstetricians and Gynecologists (ACOG), almost all CT scans give the baby far less radiation than the levels linked to harm. Scans of the head, neck, chest and limbs give the baby almost no radiation. Scans of the abdomen and pelvis give more, but usually still below the level of concern. Ultrasound or MRI is preferred when it can answer the question, but a CT you need should not be delayed because you’re pregnant. Always tell the staff if you are or might be pregnant.
How much radiation does the baby get?
The dose to the baby depends mostly on how close the scanned area is to the uterus. Doses for the baby are measured in milligray (mGy).
| Exam | Approximate dose to the baby (mGy) |
|---|---|
| CT head or neck | 0.001–0.01 |
| CT chest, including CT for a blood clot in the lungs | 0.01–0.66 |
| CT abdomen | 1.3–35 |
| CT pelvis | 10–50 |
| Chest X-ray | 0.0005–0.001 |
| Abdominal X-ray | 0.1–3 |
Ranges from ACOG. Modern scanners and pregnancy-adjusted protocols are often at the lower end.
For comparison, a baby receives about 1 mGy from natural background radiation over a whole pregnancy.
What dose is considered harmful?
ACOG notes that no fetal harm has been reported below 50 mGy, which is considered a conservative threshold. Effects such as birth defects, growth problems or miscarriage are linked to doses much higher than almost any diagnostic test, usually well above 100 mGy and mostly in early pregnancy.
The main remaining concern at lower doses is a small increase in childhood cancer risk. For a CT of the pelvis, this is estimated at roughly 1 extra case in about 3,000 children exposed. That’s a small risk, and it has to be weighed against the risk of missing a serious problem, such as appendicitis, a blood clot or an injury, which can be dangerous for both mother and baby.
Why ultrasound or MRI may come first
Ultrasound and MRI don’t use ionizing radiation, so they’re preferred when they can answer the question:
- Ultrasound is usually first for pregnancy concerns, gallbladder problems and many abdominal or pelvic symptoms.
- MRI without contrast is often used for suspected appendicitis or other abdominal problems when ultrasound isn’t enough.
- CT is used when it’s the fastest or best test, for example after a serious injury, for a suspected blood clot in the lungs, or when MRI isn’t available quickly.
What about CT contrast?
- IV iodinated contrast crosses the placenta. No harm to the baby has been shown in human or animal studies, but it’s used only when it helps the diagnosis.
- Oral contrast isn’t absorbed in a meaningful amount and isn’t a concern.
- MRI contrast (gadolinium) is generally avoided in pregnancy unless it’s truly necessary.
«I had a CT before I knew I was pregnant»
This happens more often than you might think, and in most cases the dose to the baby is very small.
- Tell your obstetrician which scan you had and when.
- Very early pregnancy: In the first 2 weeks after conception, radiation tends to have an «all or nothing» effect: either no effect or a very early pregnancy loss. Typical CT doses are far below the levels where this is a concern.
- Ask for a dose estimate if you’re worried. The imaging center’s medical physicist can estimate the dose to the baby from the actual scan settings.
- A diagnostic CT alone is almost never a medical reason to end a pregnancy, according to ACOG.
Breastfeeding after a CT
You can keep breastfeeding after a CT, with or without contrast. Less than 1% of the contrast passes into breast milk, and less than 1% of that is absorbed by the baby. ACOG says there’s no need to stop or to pump and discard milk. CT itself leaves no radiation in your body.
What happens at the scan
- You’ll be asked whether you are or might be pregnant before the scan. Some centers do a pregnancy test before abdominal or pelvic CT.
- If you’re pregnant, the radiologist checks the scan is needed and whether another test could work. They may adjust the scan to use the lowest dose possible and cover only the area needed.
- Lead shielding may or may not be used. For scans away from the abdomen, modern guidelines often skip it, because it can interfere with the scanner’s automatic dose control. Shielding doesn’t protect the baby from radiation scattered inside the body.
Questions to ask your doctor
- Why do I need this scan, and what could it change in my care?
- Could ultrasound or MRI answer the same question?
- Will contrast be used, and why?
- Can the scan be adjusted for pregnancy?
- If I’ve already had the scan, can a physicist estimate the dose to my baby?
From the scanner room
[TU EXPERIENCIA: cómo se pregunta por el embarazo en tu servicio (cartel, formulario, test); qué pasa cuando una paciente está embarazada; cómo tranquilizas a una paciente que descubre el embarazo después del TC.]
FAQ
Can a CT scan harm my baby?
At the doses used for diagnosis, harm is very unlikely. No fetal harm has been reported below 50 mGy, and most CT scans give far less than that, especially scans away from the belly.
Is a head or chest CT safe during pregnancy?
Yes. The baby receives almost no radiation from a CT of the head, neck or chest.
What if I had a CT before I knew I was pregnant?
Tell your obstetrician. In most cases, the dose to the baby is very small. A medical physicist can estimate it if needed.
Can I have CT contrast while pregnant?
Yes, when it’s needed for the diagnosis. No harm to babies has been shown, but it’s used only when it adds important information.
Do I need to stop breastfeeding after CT contrast?
No. You can keep breastfeeding as usual.
This article is for general information only and is not medical advice. If you are pregnant or might be, talk to your doctor before any imaging test, and always tell the imaging staff.
Sources
- ACOG Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation (2017, reaffirmed).
- ACR–SPR Practice Parameter for Imaging Pregnant or Potentially Pregnant Patients With Ionizing Radiation.
- ACR Manual on Contrast Media.
- CDC. Radiation and Pregnancy: information for clinicians and the public.
- RadiologyInfo.org (ACR/RSNA). Radiation Safety in Pregnancy.
- First10EM. Diagnostic imaging during pregnancy and lactation (summary of ACOG 723).