Ultrasound & Vaginal Ultrasound

An ultrasound exam may be one of the most exciting tests you have during pregnancy! You and your partner can actually see your growing baby. The test is a valuable tool for your doctor because it enables him or her to check for many details of fetal development. (Ultrasound, sonogram and sonography refer to the same test.)
Many doctors routinely perform ultrasound exams on their pregnant patients, but not every doctor does them with every patient. Some doctors perform ultrasounds only when there is a problem.

Ultrasound exams pose no threat to you or your baby. The possibility of adverse effects has been studied many times without any evidence of problems.

How the Test Is Performed
Ultrasound gives a 2-dimensional picture of the developing embryo or fetus (see the opposite page for information on 3-dimensional ultrasounds). It involves use of high-frequency sound waves made by applying an alternating current to a device called a transducer. The transducer sends and receives sound waves. As you lie on your back, the transducer moves over gel that has been spread over your abdomen. The transducer picks up echoes of sound waves as they bounce off the baby, then a computer translates them into a picture, similar to radar used by airplanes or ships to create a picture of the terrain under a night sky or on the ocean floor.
Before the test, you may be asked to drink 32 ounces (1 quart; almost 1 liter) of water. The water makes it easier for the technician to see your uterus. The bladder lies in front of the uterus; when your bladder is full, the uterus is pushed up and out of the pelvis area and is more visible on the ultrasound. When your bladder is empty, your uterus lies farther down in the pelvis, and it is harder to see.

Reasons for an Ultrasound
An ultrasound can help confirm or determine your due date, determine if there is one baby or multiples, and determine if major physical characteristics of the fetus are normal. You can have an ultrasound any time during pregnancy.
Whether you have an ultrasound during your pregnancy depends on several factors, including problems such as bleeding, previous problem pregnancies and your insurance coverage. Many doctors like to do at least one ultrasound during pregnancy. If your pregnancy is high risk, you may have several.
A doctor may order an ultrasound to learn vital information about a fetus's brain, spine, face, major organs, limbs or sex. An ultrasound can show where the placenta is, so it is used with other tests, such as amniocentesis. The test can also provide information on fetal growth, the condition of the umbilical cord and the amount of amniotic fluid in the uterus.

Doctors generally perform an ultrasound for the following reasons:
•    to identify an early pregnancy
•    to show the size and growth rate of the embryo or fetus
•    to measure the fetal head, abdomen or femur to determine the duration of pregnancy
•    to identify some fetuses with Down syndrome
•    to identify fetal abnormalities, such as hydrocephalus
•    to identify the location, size and maturity of the placenta
•    to identify placental abnormalities
•    to detect an IUD
•    to differentiate between miscarriage, ectopic pregnancy and normal pregnancy


If you are at least 18 weeks pregnant when you have an ultrasound, you may be able to determine the sex of your baby, but don't count on it. It isn't always possible to tell the sex if the baby has its legs crossed or is in a breech presentation. Even if your doctor makes a prediction as to the sex of your baby, keep in mind that ultrasound is only a test, and tests can sometimes be wrong.


Vaginal Ultrasound
Another type of ultrasound, called vaginal probe ultrasound or transvaginal sonography, can be helpful in evaluating problems early in pregnancy, such as possible miscarriage or ectopic pregnancy. The instrument (probe transducer or other device) is placed just inside the opening of the vagina; it does not touch the cervix and will not cause bleeding or miscarriage. This type of ultrasound sometimes gives better information earlier in pregnancy than an abdominal ultrasound.

3-Dimensional Ultrasound
A 3-dimensional ultrasound, available in some areas, provides detailed, clear pictures of the fetus in the womb. The pictures are so
clear the image almost looks like a photograph. For the pregnant woman, the test is almost the same as a regular ultrasound. The difference is that computer software translates the picture into a 3dimensional image. This advanced ultrasound is used when the doctor suspects abnormalities and wants to take a closer look; however, it is not widely available.

Ultrasound in Late Pregnancy
If you have an ultrasound exam in the 3rd trimester, your doctor is looking for particular information. Performed later in pregnancy, this test can accomplish many things:
•    evaluate the baby's size and growth
•    determine the cause of vaginal bleeding
•    determine the cause of vaginal or abdominal pain
•    detect some fetal malformations
•    monitor a high-risk pregnancy
•    measure the amount of amniotic fluid
•    determine which delivery method to use
•    determine maturity of the placenta


 

Breathing movements, body movements and muscle tone can be checked. If the baby is too big, it may need to be delivered by Cesarean section. If the baby is very small, other decisions can be made.

Other Facts about Ultrasound
You may be able to get a videotape of your ultrasound; ask about it when your test is scheduled to find out if you need to bring a videocassette. Most ultrasounds include black-and-white photos you may keep.

The cost of an ultrasound varies. An average cost is about $150 but can range from $100 to $300. With many insurance plans, ultrasound is an extra-not part of the normal fee for prenatal care. Ask about cost and coverage before having an ultrasound. Some insurance plans require preapproval for the test.

You can usually take your partner with you to the exam, so arrange to have the ultrasound when he can join you. You may want others to come, such as your mother or older children. Ask if that is possible when you schedule your ultrasound.