How many ultrasounds are safe during pregnancy, and can the prenatal tests harm a fetus? Our experts will put your mind at ease.

By Lisa Milbrand and Nicole Harris
Updated November 26, 2019

Many pregnant women have concerns about the safety of ultrasounds on their growing fetus. Rest assured, though, that the majority of studies indicate that limited use of ultrasounds during pregnancy won't hurt a baby. Here’s what expectant parents need to know. 

How Do Ultrasounds Work?

To understand the safety of ultrasounds, it helps to learn how they work. Ultrasounds send sound waves through the body to glimpse a baby's tissues and organs. They’re especially useful for observing fetal development, and they can detect abnormalities in the womb—including some that can be addressed before your baby is born "There is a much higher likelihood that birth defects of all types will be identified by ultrasound," says Bart Putterman, M.D., an OB-GYN at Texas Children's Pavilion for Women in Houston.

During the 15- to 30-minute procedure, the sonographer (someone trained to do ultrasounds) rubs gel on your abdomen. He/she then uses a special wand called a transducer that emits the sound waves to create pictures of your baby on the screen. 

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Are Ultrasounds Safe for Baby?

According to both the U.S. Food and Drug Administration (FDA) and the American College of Obstetricians and Gynecologists (ACOG), there’s no evidence that ultrasounds harm a developing fetus. The exams don’t use radiation or x-rays. What’s more, “no links have been found between ultrasound and birth defects, childhood cancer, or developmental problems later in life,” according to ACOG

But there’s also a catch: scientists aren’t sure if non-medical long-term ultrasound exposure is dangerous. The main concern is that energy from ultrasound waves heats up the tissues in your growing baby, and this might somehow affect her (thought his claim hasn’t been proven). "ACOG makes it very clear that the energy delivered to the fetus cannot be assumed to be completely safe," says Michele Hakakha, M.D., an OB-GYN in Beverly Hills and author of Expecting 411. "The possibility exists that some ill effects may occur when ultrasound is used inappropriately."

So how many ultrasounds are safe during pregnancy? There’s no clear answer, but despite the very slight possibility of risks, most experts agree that medically necessary ultrasounds are nothing to worry about.

Are 3D and 4D Ultrasounds Safe? 

Some doctors use 3D ultrasounds to provide pictures of the baby with clear, photograph-quality details. Others have 4D ultrasounds with video capabilities, which let you see moving images of your baby in the womb. There are many benefits to these types of exams; for example, the high-quality imaging can help doctors better diagnose certain defects, says Dr. Hakakha

Like their traditional two-dimensional counterparts, 3D and 4D ultrasounds are considered safe, as long as they’re conducted by a certified professional based on medical recommendation. Parents shouldn’t get a 3D or 4D ultrasound to simply have a “better look” at their baby’s face, says Dr. Hakakha. They should also avoid commercial shops that offer “keepsake" 3D ultrasound images and videos. 

"Ultrasounds should be done only when medical information about pregnancy is needed, and should be done only at the lowest possible setting," says Dr. Hakakha. "Ultrasounds at the mall, administered by a technician of unknown training using a machine of unknown calibration and safety, done for an unknown duration of time in order to get a picture of a fetus' face, may be dangerous." In fact, the U.S. Food and Drug Administration also issued an update in December 2014 urging consumers to avoid these fetal "keepsake" ultrasound images and videos, as well as heartbeat monitors.

The Bottom Line

"Ultrasound has been in use during pregnancy for the past 35 to 40 years, and it has an extremely good safety record," says Dr. Putterman, adding that there's "no scientific data that indicate that ultrasound examinations are harmful for mothers or developing fetuses." Still, experts recommend that you have ultrasounds only when medically necessary‚ and that means that you should avoid those commercial ultrasound shops. Only visit a trained professional who can interpret the results with accuracy and can detect abnormalities. Your technician should be schooled in obstetrical ultrasound, preferably at a center accredited by the American Institute of Ultrasound in Medicine

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