An ultrasound is a diagnostic or screening procedure that uses high-frequency sound waves to create a picture of internal body structures, such as a developing fetus. Also called an ultrasound scan, sonogram, or ultrasonography (fig. 1).
What Is It?
Ultrasound uses high-frequency sound waves to detect internal body structures, much like sonar aboard a ship can locate a school of dolphins.
An instrument called a transducer emits sound waves that bounce or echo off internal organs (fig. 2). This information is relayed to a computer, which produces an image on a nearby screen.
The routine use of ultrasound during pregnancy is somewhat controversial. Some health professionals believe it should be used to screen every pregnant woman for potential problems, while others say it should be reserved for use as a diagnostic tool when other tests or exams raise concerns.
Ultrasound Is Often Used To:
- Confirm a pregnancy.
- Spot multiple fetuses (twins, triplets, or more).
- Assess the fetus' age, size, maturity, or condition (fig. 3).
- Monitor the fetus' growth.
- Detect conditions such as spina bifida or malformations of the kidney, heart, intestines, and limbs.
- Detect poly- or oligohydramnios, the presence of too much or too little amniotic fluid.
- Assess the fetus' position (see delivery presentations).
- Identify the location of the placenta.
- Guide procedures such as amniocentesis, Percutaneous Umbilical Cord Blood Sampling (PUBS), or Chorionic Villus Sampling (CVS).
How Can I Prepare?
A full bladder helps your doctor or technician get a clearer picture of the baby (especially during the early months of pregnancy), so she may ask you to drink a lot of water and refrain from urinating for an hour or two before the ultrasound.
What Will Happen?
Ultrasound is done at your doctor's office or a hospital. You'll change into a hospital gown or simply roll your skirt or pants away from your belly and lie on your back on an exam table. Next, the technician spreads a special conducting gel on your belly and passes a hand-held transducer over it using gentle pressure. For ultrasounds done very early in pregnancy before the uterus rises up over the pelvic bone, or when the doctor needs to get a better look at the cervix, a tampon-sized transducer is inserted into the vagina.
The technician (along with your doctor) will review the images of your uterus and fetus on the computer screen, and she may even print out an image or two as a keepsake for you. Ultrasound images are hard for the untrained eye to decipher, so don't be shy about asking the technician to translate the picture for you. The entire process usually takes just a few minutes, and you shouldn't feel any discomfort while it's happening.
An ultrasound can supply vital information about your pregnancy and your baby's health. If a problem is revealed, it may also provide insight into possible treatment options. Of course, the chance that an ultrasound will correctly identify - or rule out - a particular medical condition depends on many different factors, not least of which is the skill of the person performing the procedure.
What Are The Risks?
There are no health risks associated with ultrasound, although no one knows for sure what the possible long-term effects may be for you or your child.
Frequently Asked Questions
Q: Do I have to have an ultrasound during my pregnancy?
A: Having an ultrasound is optional, though your doctor may strongly suggest that you get one if she suspects a problem.
Q: Does ultrasound use radiation?
A: No. Since it uses sound waves to create an internal image, an ultrasound is a much safer diagnostic tool during pregnancy than an X-ray.
Q: Will an ultrasound tell me if I'm having a boy or a girl?
A: If it's done at 18 weeks or later, ultrasound may pick up a clear image of your baby's genitals - provided he (or she) cooperates, of course.
Review Date: June 29, 2001
Reviewed By: Peter Chen, M.D., Obstetrics and Gynecology, University of
Pennsylvania School of Medicine. Review provided by VeriMed Healthcare
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