Prenatal Sonograms

Prenatal Sonograms

What is ultrasound?
Ultrasound is energy in the form of sound waves. The most common type of ultrasound exam is called two-dimensional (2D) ultrasound. In this type of ultrasound, a transducer sends sound waves through the body. The sound waves hit tissues, body fluids, and bones. The waves then bounce back, like echoes. The transducer receives these echoes, which are converted into images of the internal organs and—during pregnancy—the fetus.

How is ultrasound used in women’s health care?
Ultrasound can be used to diagnose and monitor certain problems, such as a pelvic mass, a breast lump, abnormal bleeding, pelvic pain, or infertility.

Where is an ultrasound exam done?
An ultrasound exam may be done in a health care provider’s office or a hospital.

Who performs the ultrasound exam?
It may be performed by your health care provider or a specially trained technician.

How is the ultrasound exam performed?
During an ultrasound exam, the transducer is either moved across your abdomen (transabdominal ultrasound) or placed in your vagina (transvaginal ultrasound).

What type of ultrasound exam will I have?
The type of ultrasound exam you have depends on what types of images your health care provider needs and why the exam is being done. If you are pregnant, it also depends on how far along you are in your pregnancy. Transvaginal ultrasound often is used in early pregnancy. Transabdominal ultrasound often is used after about 10 weeks of pregnancy. Your weight also can determine which type of exam is needed.

How is ultrasound used during pregnancy?
Ultrasound is used during pregnancy to find out whether the growing fetus inside your uterus is developing normally. It can be used to check the anatomy of the fetus for defects or problems. It also can be used to find out the following information:

  • Age of the fetus
  • Location of the placenta
  • Fetal position, movement, breathing, and heart rate
  • Amount of amniotic fluid in the uterus
  • Number of fetuses
Ultrasound may be used to screen for certain birth defects, such as Down syndrome. Ultrasound also is used during chorionic villus sampling and amniocentesis to help guide these procedures.

How many ultrasound exams will I have during my pregnancy?
You may have at least one standard exam during your pregnancy. This ultrasound exam usually is performed at about 16–20 weeks of pregnancy. Some women may have an ultrasound exam in the first trimester of pregnancy. If a problem occurs during pregnancy, such as bleeding or pelvic pain, ultrasound may be used to help find the cause.

What do I need to do to prepare for a transabdominal ultrasound exam?
If you are having a transabdominal ultrasound exam, wear loose-fitting clothes. This will allow your abdomen to be exposed easily. You may need to drink several glasses of water during the 2 hours before your exam. This will make your bladder full. A full bladder is helpful because sound waves pass more easily through liquid than through air.

What happens during a transabdominal ultrasound exam?
For this exam, you will lie on a table with your abdomen exposed from the lower part of the ribs to the hips. A gel is applied to the surface of the abdomen. This improves contact of the transducer with the skin surface. The handheld transducer then is moved along the abdomen.

What happens during a transvaginal ultrasound exam?
For a transvaginal ultrasound exam, you will be asked to change into a hospital gown or undress from the waist down. You do not need to fill your bladder before the test. You will lie on your back with your feet in stirrups, like for a pelvic exam. The transducer for this exam is shaped like a wand. It is covered with a latex sheath, like a condom, and lubricated before it is inserted into the vagina.

What is a specialized ultrasound exam?
A specialized ultrasound exam often uses additional technology to examine a particular organ. If your health care provider suspects a problem based on other tests, you may have a specialized ultrasound exam.

What are 3D and 4D ultrasound?
In a 3D ultrasound exam, multiple 2D images are taken at various angles. The images then are assembled into a 3D image. A 4D image is similar to a 3D image, but it shows movement. A 3D or 4D ultrasound sometimes is done when a specific problem is suspected during pregnancy, such as a problem with the placenta or fetus.

What are the risks of ultrasound exams?
Currently, there is no reliable evidence that ultrasound is harmful to a developing fetus. No links have been found between ultrasound and birth defects, childhood cancer, or developmental problems later in life. However, it is possible that effects could be identified in the future. For this reason, it is recommended that ultrasound exams be performed only for medical reasons by qualified health care providers.

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