FAQ Ultrasound

“What is an ultrasound? How does it work?” Ultrasound is a procedure that uses high-frequency sound waves produced by a small hand held device called a transducer to view internal organs and produce images of the body. Ultrasonic waves are inaudible and cause no sensation. The sound waves produced by the transducer cannot penetrate air, so gel is applied to help eliminate air pockets between the transducer and the skin. The technologist who performs the exam presses the transducer firmly against the skin and sweeps it back and forth to image the area of interest.
Some of the sound waves that pass through the body bounce back and are captured by the transducer. These “echoes” are then processed by a computer which generates an image.
Ultrasound technology was originally developed as sonar to track submarines during WWI. It has been used medically since the 1950s.
“How long will my test take?” The length of time varies with the type of exam. Exams typically vary from 30 to 90 minutes. At the time you make your appointment, our staff will be able to give you an estimate on the amount of time to allow for the procedure as well as the appropriate preparation necessary for your particular exam.
“How do I prepare for my ultrasound exam?” Upon scheduling your appointment, our staff will give you instructions on how to prepare for your specific exam. In certain cases, no preparation is necessary. However, if you are given preparation instructions it is important for you to follow them in order to ensure the best quality scan and the most accurate results. Please also inform our staff if you had any previous examinations of the same body part so our physician can use them for comparison.
“When will I get my results?” Your ultrasound images will be analyzed by a radiologist, a physician who specializes in the interpretation of diagnostic imaging studies. The radiologist will produce a report of the findings based on these images. A signed report will be faxed to your referring doctor’s office within 24 to 48 hours. You may obtain your results by contacting your doctor who referred you for the exam.
“Besides OB, what other types of ultrasound exams do you perform?” Ultrasound imaging is used extensively for evaluating the abdominal organs (kidneys, liver, gallbladder, pancreas, and spleen), the non-gravid uterus, breast, thyroid, testicles as well as studies of the major blood vessels.
“Why do I have to fast for an abdominal ultrasound?” Ultrasound waves do not pass through air. Eating or drinking contracts the gallbladder, making it difficult to visualize, and also produces intestinal gas which prevents or significantly limits the visualization of abdominal structures. While some abdominal gas is always present, fasting before the exam ensures for the best scan possible.
“Why do I have to have a full bladder for a pelvic ultrasound?” Two methods are used for performing a pelvis ultrasound, trans-abdominally (the probe is placed on top of the abdomen) and endovaginally (a special probe is placed inside the vagina). A full bladder is usually necessary when the scan is done transabdominally. A full bladder displaces bowel and acts as a window for the ultrasound waves to pass through to visualize the pelvic organs. Ultrasound doesn’t go through air (gas in the bowel) but transmits well through liquid (as in the case of the urine in the bladder). In an endovaginal scan, however, a full bladder will not be necessary.
“I had a scan early in the pregnancy and then one later on; which due date is correct?” The results of the scan performed early in pregnancy for ‘dating’ purposes will be more accurate. In the later part of pregnancy the measurements will be affected by growth variations and will no longer reflect the fetal ‘age’ correctly.
“How safe is it to have multiple OB ultrasound scans?” There is presently no evidence of a cumulative effect of ultrasound in the fetus. For standard diagnostic ultrasound, there are no known harmful effects on humans.
“When can I find out the gender of my baby? How accurate is the diagnosis of fetal gender by ultrasound?” Most of the time one should be able to tell the sex of the baby by about 20 weeks and sometimes even as early as sixteen weeks. On the other hand, visualization of any fetal part depends of a host of factors such as fetal position and amount of amniotic fluid. There have been occasions when gender cannot be determined even at 28 weeks.
Accuracy is usually somewhere between 95 and 100 percent, particularly after about 20 weeks. However, the technologist may not always get a good view of the fetus for a variety of reasons, and therefore the actual sex of your baby might differ from the apparent sex of your baby on the images obtained.