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Magnetic resonance imaging (MRI) is a valuable diagnostic tool, but pregnancy raises understandable safety concerns. Research from leading medical organizations, including the American College of Obstetricians and Gynecologists (ACOG) and the American College of Radiology (ACR), supports MRI as safe for use during pregnancy when medically necessary (ACOG, 2017). Here’s what the evidence says.
Key Takeaways
- MRI does not use ionizing radiation and does not expose the fetus to X-rays.
- MRI without contrast is considered safe during all stages of pregnancy when clinically indicated.
- Gadolinium contrast is avoided during pregnancy except in rare situations where diagnostic benefit outweighs risk.
- Large studies show no association between prenatal MRI exposure and miscarriage, birth defects, or childhood developmental problems.
- Ultrasound remains the first-line imaging choice, with MRI used when additional detail is required.
What Is an MRI and How Does It Work During Pregnancy?
An MRI uses magnetic fields and radiofrequency energy to create detailed images of internal organs and soft tissues. Unlike X-rays and CT scans, MRI does not involve ionizing radiation, reducing imaging-related risks during pregnancy.
During pregnancy, MRI functions the same as it does for non-pregnant patients by aligning hydrogen atoms in the body and measuring the signals released as they return to their baseline. This allows clinicians to evaluate maternal organs and fetal anatomy without exposing them to radiation, as documented in ACR safety guidance by Kanal E, Barkovich AJ, Bell C, et al. (2013) in the document titled “ACR guidance document for safe MR practices: 2007.”
Is an MRI Safe for Pregnant Women in All Trimesters?
Yes, MRI without contrast is considered safe during the first, second, and third trimesters when medically necessary. A study by Ray JG, Vermeulen MJ, et al. 2016, titled “Association Between MRI Exposure During Pregnancy and Fetal and Childhood Outcomes,” shows that MRI is safe for pregnant women in any trimester when performed without contrast, and no adverse effects on fetal development have been documented. ACOG and ACR state that MRI can be performed in the first, second, or third trimester if the benefits outweigh any theoretical risks.
In the first trimester, there is a theoretical concern about fetal heating from radiofrequency energy, but clinical data have not demonstrated harm. Scanners use “Normal Operating Mode” to limit heating and acoustic noise.
When Might You Need an MRI During Pregnancy?
MRI is ordered during pregnancy when an ultrasound does not provide sufficient diagnostic detail. Physicians rely on MRI to evaluate complex maternal conditions or fetal abnormalities that require high-resolution imaging.
Common indications include assessment of the maternal brain or spine, abdominal or pelvic pathology, and detailed evaluation of fetal anatomy when ultrasound imaging is limited by fetal position, body habitus, or gestational age.
What Adjustments Are Made to MRI Procedures for Pregnant Patients?
The following adjustments are made to MRI procedures for pregnant patients:
- Safety settings: Scanners are set to “Normal Operating Mode” to limit tissue heating (specific absorption rate) and keep acoustic noise within safe levels for the fetus.
- Positioning: Later in pregnancy, patients are positioned slightly on their side to prevent compression of the vena cava, which can reduce blood flow.
- Contrast agents are avoided: Gadolinium-based agents are withheld due to potential fetal exposure, and are only used when the benefits clearly outweigh the risks.
- Scan protocols: Imaging sequences are optimized to reduce total scan time while still providing diagnostic-quality images.
These modifications ensure the mother receives accurate diagnostic imaging while minimizing any potential theoretical risks to the developing baby, something not necessary in non-pregnant MRI protocols.
Is MRI Contrast (Gadolinium) Safe During Pregnancy?
No, MRI contrast (gadolinium) is not considered safe for routine use during pregnancy. It crosses the placenta and enters fetal circulation, and while definitive harm has not been proven, studies suggest potential risks. It is only used when the expected diagnostic benefit clearly outweighs the theoretical risks, and this decision is made jointly by the patient, radiologist, and referring physician with informed consent.
The American College of Radiology (ACR) advises against routine use during pregnancy due to this uncertainty. It is only administered if the diagnostic benefit clearly outweighs the theoretical risks, with informed consent from the patient.
Are There Risks to the Mother or Baby From MRI Scans?
No, there is no risk to the mother or baby from MRI scans. The American College of Obstetricians and Gynecologists (ACOG) notes that after 30 years of use and in thousands of cases, there is no demonstrated connection between aspirin use and these adverse pregnancy outcomes.
Possible non-harmful issues to the mother or baby from MRI scans include:
- Claustrophobia or anxiety in the enclosed scanner.
- Loud noise, managed with earplugs or headphones.
- Mild warmth from radiofrequency energy is minimized by standard safety settings.
Does an MRI Use Radiation?
No, MRI doesn’t use radiation. MRI uses magnetic fields and radio waves to create images. This is a key reason MRI is preferred over CT scans during pregnancy when high-quality imaging of soft tissues is required.
Could MRI Affect Miscarriage, Birth Defects, or Child Development?
No, current evidence does not show that MRI during pregnancy increases the risk of miscarriage, birth defects, or developmental problems in children. Studies by MotherToBaby, 2022, have found no link between MRI exposure and miscarriage, and large-scale research by Ray JG et al., 2016, involving over 1,700 first-trimester exposures reported no increase in birth defect risk.
Concerns about fetal hearing due to MRI noise have been investigated, with small studies by Zvi E, et al. 2020, titled “Fetal Exposure to MR Imaging: Long-Term Neurodevelopmental Outcome,” showing no evidence of hearing damage in utero. While data on long-term behavioral or learning outcomes are limited, no existing research has demonstrated adverse developmental effects from an MRI performed during pregnancy.
How Should You Prepare for a Full-body MRI Scan During Pregnancy?
You should do the following things to prepare for a full-body MRI scan during pregnancy:
- Wear comfortable, metal-free clothing.
- Remove jewelry, watches, and metallic objects.
- Inform the radiologist and technologist that you are pregnant.
- Complete an MRI safety questionnaire regarding implants or past surgeries.
This preparation ensures both maternal and fetal safety during the scan.
What Happens During a Full-body MRI Scan?
During a full-body MRI scan, the following things happen:
1. You will lie on a motorized table that moves into the scanner.
2. A coil (specialized equipment) may be placed over the body area being imaged.
3. The machine will make loud knocking or humming noises; ear protection is provided.
4. You must remain still for image clarity.
5. The scan lasts from 15 to 90 minutes, depending on the exam.
Are There Alternatives to MRI While Pregnant?
Yes, the following are the alternatives to MRI while pregnant:
- Ultrasound is the first-line imaging method during pregnancy because it is safe, fast, and effective for many conditions.
- CT scans can be performed in emergencies only, but because they involve radiation, they are generally avoided unless critical for maternal health.
When Should You Discuss MRI With Your Healthcare Provider?
You should discuss MRI with your healthcare provider if:
- Your doctor recommends further imaging after an ultrasound.
- You have symptoms suggesting a serious condition.
- You are concerned about the risks and benefits of contrast use.
Open communication ensures that decisions are based on accurate risk–benefit assessments for both mother and baby.
