Ultrasound is a test that gives a 2-dimensional picture of the developing embryo or fetus. It involves the use of high-frequency sound waves made by applying an alternating current to a transducer. This transducer is placed on the abdomen or in the vagina. Sound waves projected from the transducer travel through the abdomen or vagina, bounce off tissues and bounce back to the transducer. Reflected sound waves are translated into a rough picture, although the newest, most sophisticated ultrasounds show very clear pictures. These machines are new to ultrasound testing and are not in widespread use at present.
Many doctors routinely perform ultrasounds on their patients, but not every doctor does them with every patient. Some doctors perform them only when there is a definite reason for doing one.
There are three main reasons a doctor orders an ultrasound:
 | to help confirm or determine the due date by measuring the baby |
| to determine whether there is more than one baby |
| to see if major physical characteristics of the fetus are normal |
Who Has an Ultrasound?
You will not be given an ultrasound automatically. Whether you have one during your pregnancy depends on several factors, including:
| problems during pregnancy, such as bleeding |
| previous problem pregnancies |
| your healthcare provider |
| your insurance company |
Most doctors like to do at least one ultrasound during a pregnancy, but not all agree on this. If your pregnancy is "high risk," you may have several ultrasounds.
Other reasons for ultrasound.
Some other reasons for doing an ultrasound are:
| identifying an early pregnancy |
| showing the size and growth of the embryo or fetus |
| measuring the fetal head, abdomen or thighbone to determine how far along in pregnancy the woman is |
| identifying some fetuses with Down syndrome |
| identifying some fetal abnormalities, such as hydrocephalus |
| measuring the amount of amniotic fluid |
| identifying the location, the size and the maturity of the placenta |
| identifying abnormalities of the placenta |
| detecting an IUD (intrauterine device) |
| differentiating between miscarriage, ectopic pregnancy and normal pregnancy |
| helping to find a safe location to perform an amniocentesis |
| identifying a miscarriage |
How early in pregnancy you may have an ultrasound depends on problems with your pregnancy, such as bleeding or cramping. If you're having problems, your healthcare provider may want to do an ultrasound fairly early in pregnancy.
An ultrasound may help determine when your baby is due. Measurements can be taken of the baby with an ultrasound. Your doctor can compare these measurements against charts with averages to help approximate your due date.
Vaginal ultrasound.
This type of ultrasound can be helpful in evaluating problems early in pregnancy, such as possible miscarriage or an ectopic pregnancy. The instrument (a probe or transducer) is put just inside the opening of the vagina. It does not touch the cervix and will not cause bleeding or miscarriage. This type of ultrasound can sometimes give better information earlier in pregnancy than an abdominal ultrasound.
Is Ultrasound Safe?
Yes. The possibility of ultrasound having adverse effects has been studied many times without evidence that the test causes any problems.
Drink Water Beforehand
Your bladder lies in front of your uterus. When your bladder is full, your uterus is pushed up out of the pelvis and can be looked at more easily by ultrasound. When your bladder is empty, your uterus is farther down in your pelvis, where it is harder to see. The full bladder acts as a window between the outside of your abdomen and your uterus. You will probably be asked to drink 32 ounces (960ml) of water before you have the ultrasound and not to empty your bladder. With a vaginal ultrasound, your bladder doesn't have to be full.
Where Ultrasound Is Done
Some doctors have an ultrasound machine in their office and have ultrasound training. Other doctors prefer that you go to the hospital to have the ultrasound done and read by a radiologist. In certain high-risk situations, your doctor may send you to an ultrasound specialist. Ask your doctor about where your ultrasound will be done.
Videotape of Ultrasound
When your ultrasound is scheduled, ask whether you can get a videotape of the film. Not all ultrasound machines are capable of making a video recording. Ask ahead of time if you need to bring a videotape, or if your partner can videotape it.
Ultrasound Cost
Cost of this test varies, depending on where the test is done and where you live.
An average cost is about $150, but it can range from $100 to $300. With many insurance plans, ultrasound is an "extra" and not part of the normal fee for prenatal care. Ask about cost and coverage before having an ultrasound. Some insurance plans require pre-approval before an ultrasound is done.
Partner May Accompany You
The ultrasound is something your partner will probably want to see, so arrange to have the procedure when he can come. You may want others, such as your mother or older children, to come with you when possible. Ask about it when your ultrasound is scheduled.
