What is in Utero Ultrasound?

There are few things as exciting for an expectant parent as seeing the first ultrasound images of their developing baby. Ultrasound is a simple and safe technology that uses sound waves to visualize the baby in the uterus. Ultrasounds are routinely used during pregnancy for everything from monitoring the baby’s growth to determining its gender before birth and looking at the anatomy to make sure the baby is healthy. The type of ultrasound you receive depends on what the doctor is looking for.

There are two different ways ultrasound can be performed in pregnancy:

Transabdominal: During a transabdominal ultrasound, a small amount of gel is put on the skin of the abdomen, and the ultrasound probe is moved over the area, scanning the uterus.

Transvaginal: This is an internal ultrasound that involves inserting the ultrasound probe into the vagina to obtain images. This is most often done during the earliest stages of pregnancy.

Ultrasound technology has many different ways of viewing a fetus to monitor the development.

Doppler Ultrasound: This measures slight changes in the frequency of the ultrasound waves as they bounce off moving objects, such as blood cells. Doppler ultrasounds can look at a fetus’s blood flow in the heart and other parts of the body.

3-D Ultrasound: This type of ultrasound uses specially designed probes and software to generate 3-D images of the baby.

4-D or Dynamic 3-D Ultrasound: This ultrasound also uses specially designed scanners to get an even closer look at the face, anatomy, and movements of the baby prior to delivery.

Fetal Echocardiography: This type uses ultrasound waves to assess the baby’s heart anatomy and function.

How it works

A transducer produces high-frequency sound waves that bounce off bones and tissue and provide pictures of the baby.

When is it performed?

An ultrasound can be performed at any time during pregnancy. Many times, a woman will have a transvaginal ultrasound to confirm the pregnancy and the presence of a fetal heartbeat at the beginning of the pregnancy. Usually, a woman will then have a Level 2 ultrasound done between 18 and 22 weeks, which looks at the anatomy of the fetus in detail. Some women may have additional ultrasounds later in the pregnancy to follow the growth or position of the baby if they are deemed necessary. Your OB/GYN might suggest additional ultrasounds during this time if you:

  • Have a high-risk pregnancy, such as placenta previa, preterm labor, or other condition that could endanger the baby.
  • Have health issues, such as diabetes or high blood pressure.
  • Have had complications in a prior pregnancy.

Reviewed by Dr. Jen Lincoln, November 2018


  • National Institutes of Health
  • Prenatal Care in Your Third Trimester.
    American Pregnancy Association
  • Ultrasound Sonogram.

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