Are Ultrasound (Sonography) Scans Safe during Pregnancy?

A pregnant woman holding her x-ray ultrasound scan

Last Updated on



Antenatal ultrasound scans are performed to evaluate the baby’s position and movements in the womb. In this scan, sound waves are passed through the womb (uterus) to reflect off the baby’s body that is transformed into the baby’s pictures.





While some parents may have concerns about ultrasounds, there is apparently no conclusive evidence of harm caused by it. But this is considered a conventional view and there have been debates around it.

Concerns have also been raised about using ultrasounds for merely adoring or showcasing life-like pictures of the unborn baby. According to The Royal College of Obstetricians and Gynaecologists, ultrasounds should be restricted to medical procedures only rather than for “entertainment purposes”.




Is Ultrasound Safe during Pregnancy?

 A pregnant woman going through an ultrasound scan

The first concern you may have may be is ultrasound safe for baby? One theory suggests that when trained professionals conducted this procedure following proper guidelines there have been no reports of harm. Apparently, the heat produced during ultrasound is too little to cause any significant damage. Professionals also take measures to minimize heat build-up. Certain medical conditions require more frequent ultrasound but they are also conducted with utmost care. There are many debates around all this and there are no standards set about how many ultrasounds are safe during pregnancyThe following sections will discuss this in more details.

Can Ultrasound Scans be Harmful for your Baby?

There has apparently been no obvious indication that ultrasound can impact birth weight, cancers, dyslexia or hearing problems in the newborn. However, doubts have been raised about:





  • Heat generated: Ultrasounds produce less than 1-degree C heat. There is a medical theory that says that harm is caused only if the temperature of the scanned tissues increases by 4 degrees C (for instance, from 36 degrees C to 40 degrees C).
  • Sound waves: The sound beams create a stream of fluid that possibly imparts a mechanical force at the surface of cells. This phenomenon is still not properly understood, but there is a concern about the adverse effects.
  • Intensity: The ultrasound intensity is low and spread over a large area. There have been reports of rising intensity of machines used. Before 1992 the intensity of commercially used ultrasound machines was not more than 94 mW/cm2. There have been a 7 times rise in intensity now, of up to 720 mW/cm2.
  • Cavitation: This is a condition that affects tissues with the formation of gas pockets after birth. This is still highly debated but there are suggestions that our tissues may contain microbubbles can be affected by cavitation.

What if you Need Frequent Ultrasounds during Pregnancy?

Frequent ultrasounds are for certain medical conditions that we have discussed in another section below. So, are frequent ultrasounds safe while pregnant? It is advised to undertake frequent ultrasounds only for specific medical reasons. Otherwise, it is wise to keep it to a minimum.

What about other Types of Ultrasound Scans?

There are many types of ultrasound with varying technologies that incorporate 3D and 4D imaging. But the big question is are 3d and 4d ultrasounds?




2D ultrasound: 2D ultrasounds are the common type and considered safe because they

  • Are of low intensity
  • Spread over a large area
  • Generate little heat
  • Are spread out by the fluid that the baby floats in and its movements

3D and 4D ultrasounds: These create one complete picture from sections of 2D images and concentration of power is the same as in a 2D scan. Hence, they are also considered safe.





Doppler scans: These check whether the placenta is properly delivering oxygen and nutrients to the baby. Doppler is said to generate more heat because they focus sound beams over a small area. But to do that temperature is not raised to very high levels because:

  1. The tools used are not held in the same body area for long durations.
  2. The scan checks blood flow and the motion of blood dissipate the heat.
  3. Some scan machines can automatically reduce the power of the sound beam to minimize intensity.
  4. Handheld Dopplers and cardiotocographs (CTGs), used to hear the baby’s heartbeat, are also low intensity.

How will the Doctor Control the Heat from a Scan?

As we already mentioned before, a scan usually takes not more than thirty minutes and the doctor conducting it keeps moving the investigation tools over the tummy to minimize heat build-up. Some suggest this also makes frequent ultrasounds safe in cases where there is a medical necessity for them.




How can you Ensure that your Ultrasound is Performed Safely?

Here is some advice from experts that will help dispel your fear.

  • Use this scan for only medical purposes and not for making movies of the unborn babies for entertainment.
  • Use it frequently only for medical reasons that we have discussed in the next section.
  • Check the skills of the person conducting the scan.
  • Ensure that the operator is subjecting you to minimum total exposure time that is 30 minutes for a normal ultrasound.
  • Avoid Doppler during the first trimester.
  • If possible, check on the scanning intensities of the machines.

When does the Doctor Advice to Perform Scans Multiple Times?

You may require more frequent ultrasounds if you:





  • Carry twins or multiples
  • Have an existing medical condition that may complicate your delivery
  • Are over 35 years of age
  • Have a problem that has been detected in your previous scans
  • Have a history of miscarriages or stillbirth

Ultrasounds are a medically endorsed way to look into the pregnancy and see how your little one is coming along. The benefits of the ultrasounds weigh out the possible risks in cases where your pregnancy requires monitoring. However, it is safe to address any concerns you may have about this with your doctor.