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Pregnancy ultrasound    See images

Overview | Risks | Results

Alternative names:

Pregnancy sonogram; Obstetric ultrasonography; Obstetric sonogram; Ultrasound - pregnancy

Definition:

Pregnancy ultrasound is a method of imaging the fetus and the female pelvic organs during pregnancy. The ultrasound machine sends out high-frequency sound waves, which reflect off body structures to create a picture.

How the Test is Performed

You will be lying down for the procedure. A clear, water-based conducting gel is applied to the skin over the area being examined to help with the transmission of the sound waves. The ultrasound transducer (a hand-held probe) is then moved over the abdomen and pelvis. This is the conventional transabdominal technique.

How to Prepare for the Test

You will need to drink 2 to 3 glasses of liquid 1 hour before the test. You may not urinate before the examination.

How the Test will Feel

There may be some discomfort from the full bladder. The conducting gel may feel slightly cold and wet.

Why the Test is Performed

There is no definitive rule as to the number of scans a woman should have during her pregnancy. Some physicians will order an ultrasound when an abnormality is suspected on clinical grounds, while others advocate screening ultrasounds. You should consult your health care provider to determine the most appropriate scanning schedule for you.

Scans may be performed in the first trimester to:

• Confirm a normal intra-uterine pregnancy
• Assess fetal age
• Exclude abnormalities such as ectopic pregnancies or threatened abortion
• Assess fetal heart activity
• Determine the presence of multiple pregnancies
• Identify abnormalities of the placenta, uterus, and other pelvic structures

Scans may also be obtained in the second and third trimesters to:

• Assess fetal age, growth and position
• Identify congenital malformations
• Exclude multiple pregnancies
• Evaluate the placenta, amniotic fluid, and remaining structures of the pelvis

Some centers are now performing a scan at around 13-14 weeks of pregnancy to measure the thickness of the "nuchal fold" (skin on the back of the fetal neck), also known as nuchal translucency, for the purpose of evaluating the risk for Down Syndrome.

The total number of scans will vary depending on whether a previous scan has detected abnormalities that require follow-up assessment.

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