Obstetrical Ultrasound

Ultrasound uses sound waves to create images that represent slices through the body. No radiation is used in ultrasound imaging. The sound waves used are not of the pitch or frequency that humans can hear. The sound waves are generated by the ultrasound machine and are sent into the body by a transducer. The sound is then reflected, like an echo. The echo returns to the transducer and is converted into an image.

An obstetrical ultrasound is used to look at the fetus, placenta and uterus. An ultrasound of the fetus can determine such things as: number of fetuses, age of fetus, fetal position, how the fetus is growing and the gender (sex) of the fetus. Ultrasound can be used to detect some possible birth defects.

Exam Preparation

Please check in at the Main Lobby before reporting to the Radiology Department if you have not been preregistered over the phone.

It is essential to have a full bladder for the exam. This may be accomplished by drinking about 4 to 6 full glasses of water about an hour before the exam. A full bladder will enhance the sound wave transmission and provide a clear window for viewing the uterus and baby.

During the Exam

The ultrasound will be performed by a registered diagnostic medical sonographer, who is specially educated, trained and certified.

You will be asked to lie on your back on an examining table and your lower abdominal/pelvic area will be exposed. The sonographer will apply a warmed gel to the skin of the lower abdominal area. The gel allows transmission of sound waves. The gel may feel greasy, but it wipes off easily and does not stain clothing. The sonographer will move the transducer (or ultrasound probe) over the lower abdominal and pelvic area to demonstrate the baby, the mother's uterus and other structures. In some cases, you may be asked to empty your bladder part way or completely and then have additional scanning performed.

In some cases, especially for early pregnancies, a second phase of the exam, a vaginal exam, will be performed. For the vaginal phase, you will be allowed to empty your bladder. The transducer is then covered, lubricated and inserted into the vagina. Additional images of the baby, uterus or other structures will be obtained this way. The transducer is smaller than most speculums used for a vaginal exam or pap smear, but may feel similar. Most women do not find this phase of the exam particularly uncomfortable. In some cases, a radiologist may enter the room to assist in performing the exam.


Once the study is completed, the images will be studied and interpreted by a radiologist, who will send a report on the ultrasound exam and its findings to your physician.