Prenatal Ultrasound Safety: How It’s Regulated and Why It Matters

Black and white prenatal ultrasound images

Have you recently found out you’re expecting? You likely have many questions, especially when it comes to scheduling ultrasound appointments to monitor your baby’s health and development. 

One common myth that sometimes surfaces online is the idea that obstetric (i.e. prenatal) ultrasounds, especially early in pregnancy, are done without any official safety guidelines. 

This can be unsettling and even frightening to hear when you’re focused on protecting your growing baby.

The truth is that obstetric ultrasound is a highly regulated and closely monitored diagnostic tool in modern medicine. Its safety is supported by a robust framework of federal oversight, international standards, and professional clinical guidelines. 

Together, these systems ensure that ultrasound is used safely and responsibly throughout pregnancy.

What Is Obstetric Ultrasound?

Obstetric ultrasound is a non-invasive imaging technique that uses high-frequency sound waves to produce real-time images of a fetus inside the uterus. It is widely used during pregnancy to:

• Confirm gestational age and fetal viability

• Monitor fetal growth and development

• Detect structural abnormalities

• Assess placental location and amniotic fluid levels

There are several types of obstetric ultrasound:

• B-mode (brightness mode): The standard 2D, black-and-white imaging used in most prenatal scans

• M-mode (motion mode): Captures movement, often used to assess fetal heart rate

• Doppler ultrasound: Measures blood flow in the umbilical cord, placenta, or fetal heart

• 3D/4D ultrasound: Provides surface renderings and live-motion images, typically used in later pregnancy for bonding or more detailed anatomical views

Unlike imaging technologies such as X-rays or CT scans, ultrasound does not use ionizing radiation. Instead, it relies on sound energy, which makes it a preferred option for monitoring pregnancy. That said, like any medical tool, it must be used with intention and care to ensure safety, especially when imaging sensitive fetal tissue.

The good news is that strong safety protocols exist at every level of care, from how ultrasound machines are built to how they’re used in practice.

FDA Oversight: How Ultrasound Devices Are Regulated in the U.S.

In the United States, the Food and Drug Administration (FDA) classifies diagnostic ultrasound systems as medical devices. Before any system can be used in clinical practice, it must be reviewed and cleared through the 510(k) premarket notification process, unless it meets certain exemption requirements. 

This process requires manufacturers to demonstrate that the new device is substantially equivalent to an existing legally marketed device.

The review includes comprehensive documentation on the machine’s performance, safety features, and quality controls. These requirements ensure that every approved device meets a baseline of safety before it reaches patients.

The Output Display Standard: Real-Time Safety Monitoring

A key safety feature evaluated by the FDA is whether an ultrasound machine follows the Output Display Standard (ODS), a voluntary guideline introduced in the 1990s to help clinicians monitor acoustic energy during a scan.

Ultrasound systems that follow the ODS display two important safety indicators in real time:

• Mechanical Index (MI): Indicates the potential for mechanical effects from the ultrasound waves, such as tiny pressure fluctuations or the formation of microscopic bubbles in tissues

• Thermal Index (TI): Estimates the likelihood of a small temperature increase in body tissues due to the absorption of ultrasound energy

By showing these values on screen, the ODS gives sonographers and physicians the ability to monitor output levels and make informed adjustments during the scan. This supports safe practice under the ALARA principle—“As Low As Reasonably Achievable”—which encourages minimizing exposure while still obtaining the information needed.

Track 1 and Track 3 devices: Two FDA pathways for acoustic output

The FDA provides two regulatory pathways* depending on whether the device displays MI and TI in real time:

• Track 1 devices do not display MI or TI but are instead limited to preset, conservative acoustic output levels. Manufacturers must include detailed safety instructions in the user manual to ensure clinicians operate within safe boundaries.

• Track 3 devices do conform to the Output Display Standard, displaying MI and TI in real time. These devices may operate at slightly higher acoustic outputs, but only with the understanding that trained professionals will monitor those values and adjust technique as needed to maintain safety.

This tiered system ensures that all ultrasound devices operate within safe limits while offering more flexibility for skilled users who follow the ALARA principle.

*For historical reasons, the FDA's classification system skips Track 2, recognizing only Tracks 1 and 3.

International Standards: The IEC 60601 Series

Beyond U.S. regulations, ultrasound safety is also governed by international engineering and electrical safety standards. The International Electrotechnical Commission (IEC) developed the IEC 60601 series, a comprehensive set of safety and performance guidelines for medical electrical equipment, including diagnostic ultrasound systems.

These standards help ensure devices are:

• Electrically and mechanically safe

• Electromagnetically compatible with other medical equipment

• Built to perform consistently across a variety of clinical conditions

IEC 60601-2-37 is particularly relevant to ultrasounds. It addresses specific safety and testing requirements for ultrasonic diagnostic equipment. Compliance with these standards is required in many countries, including the U.S., and gives added assurance that equipment used in prenatal care meets globally recognized safety thresholds.

Professional Guidelines: How Experts Direct Safe Ultrasound Use

Medical professionals do not rely on equipment design alone to ensure patient safety. They also follow detailed clinical guidelines developed by leading, non-biased organizations. Just a few of these include:

• The American Institute of Ultrasound in Medicine (AIUM)

• The American College of Obstetricians and Gynecologists (ACOG)

• The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG)

These organizations provide guidance grounded in decades of clinical experience and supported by evolving scientific research. Their recommendations are rooted in the ALARA principle, which helps clinicians use ultrasound energy thoughtfully while still obtaining necessary information.

In addition to B-mode imaging—the most common type used in routine pregnancy scans—these guidelines also address the use of specialized techniques, such as Doppler ultrasound. Doppler is especially useful for evaluating blood flow in fetal vessels, the placenta, or the heart. However, pulsed Doppler ultrasound, including spectral Doppler, operates at a higher acoustic output compared to standard imaging modes.

Because developing fetal tissues are more sensitive in the first trimester, the AIUM advises that spectral Doppler should only be used early in pregnancy when there is a clear medical reason. In these cases, professionals are trained to monitor the Thermal Index (TI) and use the lowest output settings possible—ideally keeping the TI below 1.0—to reduce the potential for tissue heating.

These types of recommendations are part of routine training for sonographers and are reinforced through credentialing, continuing education, and clinical quality standards. By following them consistently, providers are able to use ultrasound safely and effectively throughout each stage of pregnancy.

Why Prenatal Ultrasound Safety Myths Persist

Despite the existence of clear, detailed guidelines and regulatory processes, misinformation about prenatal ultrasound safety continues to circulate. This is often due to misunderstandings about how the technology works or a lack of awareness around the oversight involved.

Ultrasound is the most commonly used imaging technique for assessing the fetus throughout pregnancy. With multiple layers of regulation—from the FDA to international manufacturing standards to clinical practice guidelines—it remains a trusted tool in prenatal care.

By understanding how these systems work together to prioritize safety, expectant parents can feel more confident in the care they receive.

Safe Ultrasound Imaging for New Orleans Families

At Nola Diagnostic Ultrasound, patient safety is always our priority. 

We follow all federal regulations and professional recommendations to ensure every scan is performed with the highest standard of care. Our sonographer is trained to monitor and apply MI and TI values according to current best practices, using up-to-date equipment that meets national and international safety guidelines.

We’re committed to making your experience clear, informed, and comfortable because your peace of mind matters as much as the accuracy of your results.

Book your prenatal ultrasound in New Orleans with a provider dedicated to safe, evidence-based care.