Ultrasound

What is an ultrasound?

An ultrasound scan is a diagnostic technique which uses high-frequency sound waves to create an image of the internal organs. Ultrasounds are done during the course of a pregnancy to verify the due date, look at fetal anatomy, and monitor fetal growth. Ultrasounds may be performed at various times throughout pregnancy for different reasons:

In the first trimester:

to establish the dates of a pregnancy
to determine the number of fetuses and identify placental structures
to diagnose an ectopic pregnancy or miscarriage
to examine the uterus and other pelvic anatomy
in some cases to detect fetal abnormalities

Mid-trimester: (sometimes called the 18 to 20 week or level 2 scan)

to confirm pregnancy dates
to determine the number of fetuses and examine the placental structures
to assist in prenatal tests such as an amniocentesis
to examine the fetal anatomy for presence of abnormalities
to check the amount of amniotic fluid
to examine the placenta
to measure the length of the cervix
to monitor fetal growth

Third trimester:

to examine blood flow patterns
to observe fetal behavior and activity
to monitor fetal growth
to check the amount of amniotic fluid
as part of other testing such as the biophysical profile
to determine the position of a fetus
to assess the placenta

How is an ultrasound scan performed?

Although the specific details of each procedure vary slightly, generally, ultrasounds follow this process. Two types of ultrasounds can be performed during pregnancy:

abdominal ultrasound
In an abdominal ultrasound, gel is applied to the abdomen and the ultrasound transducer glides over the gel on the abdomen to create the image. A woman may need to have a full bladder for abdominal ultrasounds in early pregnancy. This helps move the uterus into better view.
transvaginal ultrasound
In a transvaginal ultrasound, a smaller ultrasound transducer is inserted into the vagina and rests against the back of the vagina to create an image. A transvaginal ultrasound produces a sharper image in early pregnancy.

Ultrasound images may be captured in still photographs or on video to document findings.

What are the risks and benefits of ultrasound?

There is no known evidence of any type of risk or danger to the fetus with ultrasound. The mother may experience some discomfort from the pressure of the ultrasound transducer or from having a full bladder, which may be needed in early pregnancy exams.

Ultrasound is a technique that is constantly being improved and refined. As with any test, results may not be completely accurate. However, ultrasound can provide valuable information for parents and healthcare providers to help manage and care for the pregnancy and fetus. In addition, ultrasound gives parents a unique opportunity to see their baby before birth, helping them to bond and establish an early relationship.

Topic Home Page | Return to Full List of Topics

The information on this Web page is provided for educational purposes. You understand and agree that this information is not intended to be, and should not be used as, a substitute for medical treatment by a health care professional. You agree that Lucile Salter Packard Children's Hospital is not making a diagnosis of your condition or a recommendation about the course of treatment for your particular circumstances through the use of this Web page. You agree to be solely responsible for your use of this Web page and the information contained on this page. Lucile Salter Packard Children's Hospital, its officers, directors, employees, agents, and information providers shall not be liable for any damages you may suffer or cause through your use of this page even if advised of the possibility of such damages.