Ultrasound (also called sonography or ultrasonography) is a noninvasive diagnostic imaging test. It uses high-frequency sound waves to create real-time pictures or videos of internal organs or other tissues, such as blood vessels. An ultrasound picture is called a sonogram.
Ultrasound enables healthcare providers to “see” details of soft tissues inside the body without making any incisions.

What is 3D vs. 4D ultrasound?

Most ultrasounds create flat (or two-dimensional) images. Some maternal and fetal medicine providers offer 3D or 4D ultrasounds. Both 3D and 4D ultrasounds provide a more lifelike-appearing view of your baby inside the womb. 4D ultrasound provides live motion. It shows the real-time movement of your baby (like watching a movie).

Certain factors (like having a full bladder or stomach) can make ultrasound pictures turn out more or less detailed. Your healthcare provider will give you instructions before your test to help ensure clear images.

You may not need to do anything to prepare. Or your provider may ask you to:

• Avoid using the bathroom before your scan.
• Drink a specific amount of water right before your scan.
• Stop eating or drinking a certain number of hours before having an ultrasound.

Healthcare providers often use obstetric ultrasound (also called prenatal ultrasound) to monitor a mother and baby during pregnancy. Your provider may use abdominal or transvaginal ultrasound early in pregnancy to determine:

• Your due date.
• Your baby’s well-being, including heart rate.
• How far along you are in your pregnancy (called your baby’s gestational age).
• Presence of multiples (more than one baby).
• Most doctors recommend an ultrasound at 20 weeks gestation. This test tracks your unborn baby’s growth and development during pregnancy. This ultrasound may also show your baby’s biological sex. Tell your technician if you do or do not want to know the sex.