What's The Difference Between A Sonogram And An Ultrasound? Why Do I Need One Anyway?

If you are pregnant for the first time, you probably already know that your doctor is likely to order an ultrasound of the baby at some point in your pregnancy. You may be wondering if an ultrasound is really necessary. You may also find terms like ultrasound and sonogram confusing. While the two terms refer to the same procedure, they are not exactly the same thing. Find out how they differ and why they are important to the health of your unborn baby.

What is an ultrasound?

Ultrasound is the high-frequency sound that is bounced off your unborn baby. This sound is typically 20 kHz, which means it cannot be heard by the human ear. Gel is applied to your belly, and a special wand it used to direct the sound waves at your unborn baby. This is painless for both of you.  As the sound waves bounce off tissue of differing densities, such as your baby's body parts, the machine records the time it takes for the sound to bounce back to the machine. This enables it to create a picture of your baby. 

What is a sonogram?

The picture of your baby is called a sonogram. The ultrasound technician views the image of your baby on a monitor and generally prints one or more of the images of your baby for you to add to your baby's baby book. In traditional ultrasound exams, the printed sonogram looks like an old photograph negative. 3D ultrasounds produce a more detailed image of the baby.

Why are ultrasound exams important?

Many doctors order routine ultrasounds to monitor the size and health of the baby. While some women have several ultrasounds during their pregnancy, some women don't have any ultrasounds. The decision to do an ultrasound rests with you and your doctor.

• Ultrasounds done in the first trimester are the most accurate in determining the gestational age of the fetus. Your doctor may change your due date after an ultrasound. New regulations from  the American College of Obstetricians and Gynecologists recommend that your doctor changes the expected due date if the gestational age of the fetus differs more than 5 days from your original due date in ultrasounds done before 9 weeks, or 7 days in ultrasounds performed between 9 and 14 weeks. Ultrasounds done in later trimesters do not affect the projected due date of your baby. For women with irregular menstrual cycles, an ultrasound can be invaluable in pinpointing the probable time of conception and the expected delivery time.
• Ultrasounds verify whether you are carrying one fetus or whether you will give birth to multiples.
• Ultrasounds may be performed later in the pregnancy to verify the position of the placenta, measure amniotic fluid or determine the position of the baby.
• Many couples opt for an ultrasound to determine the sex of the baby, but this isn't foolproof. The position of the baby in the womb may make it difficult to determine the sex of the fetus.
• Ultrasounds are used to monitor any special health concerns for either the mother or the baby.

How does an ultrasound determine a due date?

According to Baby2See.com, the crown-rump length (the length of the embryo), the size of embryonic sack, the size of your baby's head and the length of the femur (thigh bone) are all used to help determine the gestational age of your baby. They are most accurate in early pregnancy. Head size and femur length may be used in late pregnancy ultrasounds to help determine the size of the baby.

When will I get the results?

You can watch the monitor as the ultrasound technician performs the ultrasound. You may also receive a copy of a sonogram of your baby, but the technician cannot give you the results of the ultrasound. The ultrasound must be read by a trained professional who will send the results to your doctor. In most areas, you will receive the results of the ultrasound in a day or two.

If your doctor orders an ultrasound, talk to him about the reason for the procedure. If he uses terminology you do not understand (or are not sure about) ask him to repeat it in terms you understand. You have a right to know the reason for all tests.