What to Expect During an Obstetrical Ultrasound
For most ultrasound exams, you are positioned lying face-up on an examination table that can be tilted or moved.
A clear water-based gel is applied to the area of the body being studied to help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin.
The sonographer (ultrasound technologist) or radiologist then presses the transducer firmly against the skin and sweeps it over the area of interest.
Sometimes the radiologist determines that a transvaginal scan needs to be performed. This technique often provides more detailed images of the uterus and ovaries. This method of scanning is especially useful in early pregnancy.
Transvaginal ultrasound is performed very much like a gynecologic exam and involves the insertion of the transducer into the vagina after you empty your bladder. The tip of the transducer is smaller than the standard speculum used when performing a Pap test.
A protective cover is placed over the transducer, lubricated with a small amount of gel, and then inserted into the vagina. Only two to three inches of the transducer end are inserted into the vagina. The images are obtained from different orientations to get the best views of the uterus and ovaries. Transvaginal ultrasound is usually performed with the patient lying on her back, possibly with her feet in stirrups similar to a gynecologic exam.
Doppler sonography is performed using the same transducer.
When the examination is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed. However, the sonographer or radiologist is often able to review the ultrasound images in real-time as they are acquired and the patient can be released immediately.
An ultrasound is usually completed within 30 minutes.
Most ultrasound examinations are painless, fast and easy.
After you are positioned on the examination table, the radiologist or sonographer will apply some warm water-based gel on your skin and then place the transducer firmly against your body, moving it back and forth over the area of interest until the desired images are captured. There is usually no discomfort from pressure as the transducer is pressed against the area being examined.
If scanning is performed over an area of tenderness, you may feel pressure or minor pain from the transducer.
At times the sonographer may have to press more firmly to get closer to the embryo or fetus to better visualize the structure. Any discomfort is usually minimal and temporary.
If a Doppler ultrasound study is performed, you may actually hear pulse-like sounds that change in pitch as the blood flow is monitored and measured.
With transvaginal scanning, there may be minimal discomfort as the transducer is moved in the vagina.
Once the imaging is complete, the gel will be wiped off your skin.
After an ultrasound, you should be able to resume your normal activities within a few hours.
Limitations of Obstetrical Ultrasound
Obstetric ultrasound cannot identify all fetal abnormalities. Consequently, when there are clinical or laboratory suspicions for a possible abnormality, you may have to undergo non-radiologic testing such as amniocentesis (the evaluation of fluid taken from the sac surrounding the fetus) or chorionic villus sampling (evaluation of placental tissue) to determine the health of your fetus. You also may be referred to a perinatologist (an obstetrician specializing in high-risk pregnancies).