How an Ultrasound Technician Does Their Job

Ultrasound technician

Ultrasounds, also called sonograms, are a routine part of pregnancy check-ups. They work by using high-frequency sound waves to produce images of the fetus and give your OB/GYN information about how your baby is developing.

These tests can be performed by doctors, but are often performed by ultrasound technicians, who are not permitted to interpret the results. Ultrasound images must be interpreted by a physician.

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Your Baby's Ultrasound: What to Expect

What an Ultrasound Technician Does

Ultrasound technicians, or sonographers, are trained to operate ultrasound machines and take fetal measurements. Since they are not medical practitioners, they are not qualified to give medical diagnoses.

Unlike doctors, who attend four years of college, four years of medical school, and a residency training program, ultrasound technicians do not have a medical degree. Typically, ultrasound technicians attend a two-year associate's degree program.

Nurses and other practitioners with a medical background can take an eight-week certificate program. It is also possible to get a bachelor's or master's degree in diagnostic sonography.

These varying degree programs are typically certified by the Commission on Accreditation of Allied Health Education Programs (CAAHEP). If your sonographer has the letters RDMS after their name, it means they are a registered diagnostic medical sonographer and have passed the American Registry for Diagnostic Medical Sonography (ARDMS) exam.

Most physicians are also trained in how to operate ultrasound machines and may perform the procedure in their offices, in which case you might receive your diagnosis at the same time as your ultrasound since the images are available instantly.

If your ultrasound is being performed by a technician, the technician most likely will not be allowed to tell you what the results mean. In that case, you will have to wait for your doctor to examine the images.

Ultrasounds are used during pregnancy to measure the fetus and rule out or confirm suspected problems. Here's what these tests can do during the three trimesters of pregnancy.

First-Trimester Ultrasounds

Transvaginal ultrasound is most often used in the first trimester. In this procedure, a special transducer, covered with a condom-like sheath and a sterile lubricant, is placed in the vagina.

The practitioner moves the wand within the vaginal cavity to scan your uterus. These scans are used early in pregnancy and allow your practitioner to see the fetus before it's detectable on an abdominal ultrasound.

Ultrasounds in the first trimester are used to:

  • Confirm a viable pregnancy
  • Estimate a due date
  • Confirm a heartbeat
  • Measure the length of the baby or gestational age
  • Confirm molar or ectopic pregnancies
  • Assess abnormalities
  • Determine if a twin/multiple pregnancy is dichorionic or monochorionic

Second-Trimester Ultrasounds

A transabdominal ultrasound is most often used in second trimester ultrasounds. For this, the technician will spread gel on your abdomen. Then they will use a special wand, called a transducer, and move it around the surface of your belly to get images of the baby; these images can be seen on a computer monitor simultaneously and will be captured so that your doctor can interpret them.


In addition, something called a Doppler device may be used (also on the abdomen). This amplifies your baby's heartbeat and can alert the doctor to any abnormalities having to do with blood flow.

Ultrasounds in the second trimester are used to:

  • Confirm fetal well-being
  • Determine a baby's sex (in most, but not all cases)
  • Diagnose fetal malformation
  • Look for characteristics of Down syndrome (at 13-14 weeks)
  • Identify structural abnormalities
  • Confirm a multiples pregnancy
  • Verify proper growth
  • Confirm intrauterine death
  • Identify hydramnios or oligohydramnios (excessive or reduced levels of amniotic fluid)

Third-Trimester Ultrasounds

Transabdominal ultrasounds are most often used in the third trimester, as well. However, sometimes transvaginal ultrasounds are used later in pregnancy to determine things like placental abnormalities or the source of bleeding.

Ultrasounds in the third trimester are used to:

  • Identify the location of the placenta
  • Confirm intrauterine death
  • Observe fetal presentation
  • Observe fetal movements
  • Identify uterine and pelvic abnormalities of the mother

High-Resolution Ultrasounds

Standard ultrasounds provide two-dimensional (2D) images. Three-dimensional (3D) and four-dimensional (4D) ultrasounds are also used in certain situations. With 3D ultrasound exams, multiple two-dimensional images are taken at various angles and then pieced together to form a three-dimensional rendering.

So, for example, instead of seeing your baby's face in profile (as with 2D ultrasounds), you can see the whole surface of the face. With a 4D ultrasound, the image shows movement. As with a video, you may see your baby doing things in real time (like opening and closing her eyes or sucking her thumb).

High-resolution ultrasounds are usually only performed when a fetal anomaly—such as cleft lip or spinal cord problem, or some other abnormality—is suspected. Sometimes, your doctor will provide one solely so that you can get a preview of your baby.

While ultrasounds are non-invasive and generally considered safe, the American College of Obstetricians and Gynecologists recommends that ultrasounds be performed only for medical reasons.

4 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Radiological Society of North America. General ultrasound.

  2. American Registry for Diagnostic Medical Sonography. About ARDMS.

  3. American College of Obstetricians and Gynecologists. Ultrasound exams.

  4. Campbell S. A short history of sonography in obstetrics and gynaecologyFacts Views Vis Obgyn. 2013;5(3):213-229.

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.