What you can expect

By Mayo Clinic Staff

There are two main types of fetal ultrasound exams:

  • Transvaginal ultrasound. With this type of fetal ultrasound, a wandlike transducer is placed in your vagina to send out sound waves and gather the reflections. Transvaginal ultrasounds are used most often during early pregnancy, when the uterus and fallopian tubes are closer to the vagina than to the abdominal surface.
  • Transabdominal ultrasound. A transabdominal fetal ultrasound is done by moving a transducer — a small plastic device that sends and receives sound waves — over your abdomen. This type of fetal ultrasound is usually used during the later part of your pregnancy.

Various other types of transabdominal ultrasounds are available, including:

  • Specialized sonographic evaluation. Specialized examination might be needed in specific circumstances, such as when a fetal abnormality is known or suspected. In this situation, a more detailed evaluation can provide additional information about the abnormality.
  • 3-D ultrasound. A 3-D fetal ultrasound can provide images of a baby with photo-quality details. This type of ultrasound is sometimes used to help health care providers detect facial abnormalities or neural tube defects.
  • Doppler ultrasound. A Doppler ultrasound measures slight changes in the ultrasound waves as they bounce off moving objects, such as blood cells. A Doppler ultrasound can provide details about a baby's blood flow.
  • Fetal echocardiography. This type of fetal ultrasound provides a detailed picture of a baby's heart. It might be used to confirm or rule out a congenital heart defect.

During the exam

During a transabdominal fetal ultrasound, you'll recline on an exam table and expose your abdomen. Your health care provider or technician will apply a special gel to your abdomen. This will improve the conduction of sound waves and eliminate air between your skin and the transducer — the small plastic device that sends out sound waves and receives those that bounce back.

Your health care provider or technician will move the transducer back and forth over your abdomen. The sound waves reflected off your bones and other tissues will be converted into images on a monitor.

Your health care provider or technician will measure your baby's anatomy. He or she might print or store certain images to document important structures. You'll likely be given copies of some of the images.

Depending on your baby's position and stage of development, you might be able to make out a face, hands and fingers, or arms and legs. Don't worry if you can't "see" your baby. Ultrasound images can be hard for an untrained observer to decipher. Ask your health care provider or technician to explain what's on the screen.

The procedure for other types of fetal ultrasound exams is similar. If you're having a transvaginal ultrasound, however, you'll be asked to change into a hospital gown or undress from the waist down. You'll recline on an exam table and place your feet in stirrups. Your health care provider or technician will place a lubricated transducer in your vagina rather than moving it across your abdomen.

After the exam

You can wipe off any residual gel or lubricant. If you had a full bladder during the ultrasound, you can urinate after the exam.

Sept. 19, 2015