Ultrasound
Diagnostic ultrasound is a powerful, non-invasive medical tool.
On this page
About ultrasound
Diagnostic ultrasound operates by transmitting high-frequency sound waves (acoustic radiation) into the body at frequencies 100 - 500 times higher than what the human ear can detect. Images are then created by reception, processing, and display of echoes reflected from structures, tissues and flowing blood. The technique is similar to how bats, whales, and dolphins use echolocation, or how submarines use SONAR.
Ultrasound is used for real time imaging of the fetus, internal organs of the body, veins, arteries and blood flow. Ultrasound can be used as a form of physiotherapy treatment and as a surgical tool for destroying abnormal tissue growths or tumours.
Ultrasound is also used extensively in industrial, commercial, military and home applications such as ultrasonic drilling, welding, cleaning, alarms, and animal repellants.
There are concerns about the safety of ultrasound when it comes in contact with the human body because it is a form of energy which, above certain thresholds, can cause destructive heating and/or interaction effects with microscopic bubbles in the body. A cautious approach should therefore be taken in its use.
Fetal ultrasound
Health Canada recommends that diagnostic fetal ultrasound be done only when the expected medical benefits outweigh any foreseeable risk.
Diagnostic fetal ultrasound
Diagnostic fetal ultrasound provides medical information that will help your health care professional care for you and your baby.
Fetal ultrasound creates images of the unborn baby in the womb. The procedure uses high-frequency sound waves, transmitted in a series of focused beams that travel through the body and reflect off internal structures. Echoes from the beams are converted into real-time images that show the movement, surface features, internal organs and, with special techniques, even the blood flow of the fetus. The images are viewed on a monitor and can be stored digitally. When the procedure is used to obtain images for medical purposes, it is called diagnostic fetal ultrasound.
Diagnostic fetal ultrasound provides important medical information, such as the size, age and state of health of the baby in the womb. It can also detect a multiple pregnancy and can diagnose certain birth defects. The clinical use of fetal ultrasound has grown rapidly and it has an excellent safety record when performed by qualified health professionals. There have been millions of these examinations over the past few decades with no confirmed health risks for the baby or the mother. This finding is consistent with the majority of scientific studies on the effects of ultrasound.
Although this is very reassuring, there is also evidence suggesting that there may be a biological effect on the fetus even during diagnostic use. Research is ongoing to ensure the continued safety of diagnostic fetal ultrasound.
Diagnostic fetal ultrasound is done only on referral from a licenced health care provider. It is performed in a clinical setting by highly qualified professionals. Discuss any concerns you have with your health care provider so that you can make an informed decision about the use of fetal ultrasound during your pregnancy.
Fetal ultrasound for keepsake videos
Some businesses promote the use of fetal ultrasound machines for the sole purpose of making videos of babies in the womb as a keepsake for parents. In this setting, the ultrasound provides no information about the baby's health.
Fetal ultrasound used solely to create keepsake images or videos is discouraged because it exposes the fetus to ultrasound without any medical benefit, and the duration and technique of these sessions are not clinically controlled. Ultrasound should be performed only when medically indicated and by trained personnel who can minimize exposure while obtaining essential clinical information.
Listening to the fetal heartbeat
There are devices sold in stores and online that allow you to listen to the heartbeat of the fetus. Some of these devices use ultrasound technology and are often called fetal dopplers, doptones, or heart monitors. They use reflected ultrasound to listen for heartbeats rather than creating an image.
The use of these devices by untrained people is a safety risk to mothers and their babies. Without proper training, the sounds detected, such as the sound of the mother's heartbeat or the blood flow through the placenta, could easily be misinterpreted as the baby's heartbeat. This can result in false reassurance and lead to a delay in seeking medical attention, and death of the baby.
Furthermore, overuse or misuse of these devices may increase the potential for unnecessary fetal tissue heating. The long-term health effects of repeated or prolonged fetal exposures that may occur with non-clinical use are not known.
Health Canada recommends that these devices only be used when medically necessary by people who are trained in the clinical use of ultrasound devices. Mothers who are concerned about their baby's wellbeing are advised to seek immediate medical attention.
Health Canada's role
Health Canada regulates diagnostic ultrasound devices under the Food and Drugs Act, the Radiation Emitting Devices Act, and the Medical Devices Regulations. This ensures the safety and effectiveness of the devices when they are used for their licenced diagnostic purposes and according to guidelines for safe use.
Health Canada has established Guidelines for the Safe Use of Diagnostic Ultrasound. The Guidelines state that ultrasound should not be used for any of the following activities:
- to have a picture of the fetus, solely for non-medical reasons
- to learn the sex of the fetus, solely for non-medical reasons
- for commercial purposes, such as trade shows or producing pictures or videos of the fetus