A prenatal ultrasound test uses sound waves, inaudible to the human ear, that are beamed through the abdomen into the body, causing return echoes that are recorded and transformed into video or photographic images of the baby, amniotic sac, placenta, and ovaries.
It can be performed topically, or on the surface of the skin, using a gel as a conductive medium to aid in the quality of the image or transvaginal using a tubular probe that is inserted into the vaginal canal.
The transvaginal method is usually used early in pregnancy to determine how far along is a woman in her pregnancy (gestational age) and to determine the presence of more than one fetus.
The topical is generally performed later, for all pregnant women around 20 weeks gestation, to confirm the placenta location, the health, position and expected the weight of the baby and the amount of amniotic fluid around the baby.
Also on the ultrasound can be seen the baby's heartbeat, movement of its body and the gender of the baby, if women wish to know it. Sometimes there is a chance that the ultrasound can be misinterpreted so it is not a foolproof method to determine baby's gender.
Now available are newer ultrasounds that show a 3-dimensional view of the fetus which has clarity similar to a photograph so it can be useful in detecting birth defects. In some facilities, this scan can be performed at the parents' request without a specific medical indication.
4-d ultrasound is interpreted as a moving picture interpretation but accordingly to the FDA and many other experts, the use of these non-medical ultrasounds is discouraged since untrained personnel may provide inaccurate or harmful information.
Some doctors require that woman drink 4 to 6 glasses of water before the test, so her bladder is full and the view of the baby is better on the ultrasound.
During an ultrasound, the woman will lie on a padded examining table and the small amount of water-soluble gel, which does not harm the skin or stain on the clothes, is applied to the skin over your abdomen.
Then a small device, called a transducer, is gently applied to the skin on woman abdomen and a picture is seen on the screen. The picture can be printed and some doctors allow a woman to keep the picture or even allow a woman to videotape the ultrasound so she can take it home.
The woman should ask her doctor about this option. After an ultrasound, the gel is wiped off the woman’s skin and then she will discuss the test results with the doctor. The ultrasound test takes about 30 minutes to complete.
An ultrasound is safe and there are no harmful side effects to a woman or her baby because an ultrasound does not use radiation, as X-ray tests do.
If the ultrasound is deemed medically necessary, the insurance will pay for it but if it is not medically necessary (for example, to simply see the baby or find out the baby's sex), the insurance company may not pay for the ultrasound.