Version July 2025
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What is a prenatal ultrasound? —
This is a type of imaging test done during pregnancy (figure 1). It uses sound waves to create pictures of the inside of your body and your developing baby. The images appear on a screen during the test.
Doctors use a prenatal ultrasound to look at your uterus, your baby, and your baby's organs. Or they might do an ultrasound to look for the cause of symptoms like pelvic pain or vaginal bleeding.
During a prenatal ultrasound, they will check your:
●Uterus and cervix
●Baby
●Placenta and umbilical cord
●Amniotic fluid (the fluid surrounding the baby)
During an ultrasound, the doctor might also be able to learn the sex of your baby. They might print ultrasound pictures for you to keep.
Does everyone get an ultrasound while they are pregnant? —
Most people get at least 1 ultrasound during pregnancy. How many you need and when are based on your and your baby's health.
Doctors do ultrasounds for different things, depending on how far along you are in pregnancy. Ultrasounds done earlier in pregnancy are used to:
●Check the baby's age
●See if there is more than 1 baby (for example, twins)
●Look for problems with how the baby is developing
●Look for problems with the placenta
Ultrasounds done later in pregnancy focus more on growth and how much fluid is around the baby.
What are the different types of ultrasounds?
●A regular ultrasound creates a 2-dimensional ("2D") image and video as the baby moves.
●A "Doppler" ultrasound measures blood flow in blood vessels, including in the baby's heart.
●There are also 3-dimensional ("3D") and 4-dimensional ("4D") ultrasounds:
•Just like 2D ultrasounds, 3D and 4D ultrasounds use sound waves to create pictures. With a 3D ultrasound, the images are stacked together to create a more lifelike picture. A 4D ultrasound stacks the pictures together to create a moving image, like a video. With a 4D ultrasound, you can see your baby move, smile, or yawn while they are still in your uterus.
•3D and 4D ultrasounds show more detailed images. This can help a doctor find or confirm a problem with the baby. But they are not always covered by health insurance.
How do I prepare for a prenatal ultrasound? —
The doctor or nurse will tell you if you need to do anything special to prepare. This depends on why you are having an ultrasound and which organs they need to see.
In some cases, especially during early pregnancy, you might be asked to drink extra liquids and not use the bathroom before the test. This makes sure you have a full bladder and makes it easier to see your baby.
Later in pregnancy, you probably won't need to do anything special before the test.
What happens during a prenatal ultrasound? —
When it is time for the procedure:
●Most of the time, you will adjust your clothes to show your belly. But you might need to remove your clothes and put on a gown. You will be asked to lie down on an examination table.
●The doctor, nurse, or technician will put a small amount of gel on your skin or on a special wand called a "transducer" or "probe."
●For most ultrasounds, they will gently press the transducer against your skin and move it around to create the images. In some cases, the ultrasound probe is inserted into the vagina.
●Images will appear on a computer screen. This lets the doctor see the organs and structures inside your body as well as your baby. In some cases, color images give information about where and how fast blood is flowing.
●The test does not usually hurt. But you might feel pressure when the transducer presses against your skin. You might need to change positions or hold your breath for a few seconds during the test.
●A prenatal ultrasound usually takes about 30 minutes.
What happens after a prenatal ultrasound? —
The doctor, nurse, or technician will wipe the gel off your skin, and you will get dressed.
Your doctor will review the results and talk to you about what they mean. The results can help them learn more about your baby's development and health. You might need to have other tests or procedures.
What are the risks of a prenatal ultrasound? —
Your doctor will answer your questions. An ultrasound does not usually have any risks to your health or the health of your baby. This test does not expose you to radiation.
Patient education: Ultrasound (The Basics)
Patient education: Pelvic ultrasound (The Basics)
Patient education: Prenatal care (The Basics)
Patient education: Testing for Down syndrome during pregnancy (The Basics)
Patient education: When your baby is measuring large during pregnancy (The Basics)
Patient education: When your baby is measuring small during pregnancy (The Basics)
