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Fetal Ultrasound

Ultrasound (also called diagnostic ultrasonography or sonogram) is an extremely useful tool that utilizes high frequency sound waves to create images of a woman's uterus and the baby growing within it. Sound waves are sent through a handheld transmitter called a transducer that is gently applied to a woman's abdomen or early in pregnancy may be placed inside the vagina using a narrow probe. (Placing the ultrasound transducer inside the vagina does not pose any or either mother or baby.) The sound waves reflect back to the transducer from the internal structures in patterns that vary depending upon their shape and density. The images are displayed on a monitor and may even be recorded on videotape. (Some of the images may be printed for the expectant parents to take as their first "baby picture.")

When is it performed? Ultrasound may be carried out during any stage of pregnancy. The timing for this procedure will depend to some degree upon its purpose, the state of your pregnancy, any problems that are developing, and your physician's approach to following a normal pregnancy. Many doctors recommend routine ultrasonography between the sixteenth and twentieth weeks of pregnancy, at which point many details (including the chambers of the bacy's heart can be visualized.

How is it performed? A woman having an ultrasound will normally be instructed to drink a few glasses of water and hold off on voiding until the procedure is completed because a full bladder serves as a useful landmark. (A full bladder is not necessary for a vaginal ultrasound.) A conducting gel will be applied to the abdomen and the transducer then gently pressed against it in a number of locations. A basic evaluation, which can be carried out in the doctor's office, willally not take more than twenty minutes, while a more detailed (sometimes cal.level two) study could take an hour or more. The latter might he done if thereconcern about an abnormality for which more detailed information and sopltticated equipment are needed.

Normally you will be able to see the monitor during an ultraso•Ind, andtechnician or physician will usually point out a variety of highlights of your "tour" of the uterus and its occupant. Parents are often delighted and dee--moved by the first sight of their new child and may be surprised by the amount of movement if the baby is active at the time of the procedure.

Is it safe? Ultrasound has never been reported to cause harm to mother or ba:even during the earliest stages of pregnancy. NO X-rays are involved, and the mother's skin is not punctured. Sometimes there is mild discomfort when the transducer is pressed against a full bladder.

What information does it provide? This test can provide a great deal of information:

• Verification that pregnancy is in fact under way within the uterus. A tiny sac can be visualized three weeks after conception, and a week later the baby's body can be seen within it. Ultrasound is also useful in diagnosing an ectopic pregnancy (one that is growing in an abnormal location).

• An accurate determination of the age of the baby and whether or notmore than one baby is present.

• An assessment of the growth rate and movements of the baby.

• Detection of major structural abnormalities of the head, spinal cord,chest, abdomen, or limbs.

• The location and appearance of the placenta and the amount of amni-otic fluid.

• Identifying structures (such as the placenta) that are important to diagnos-tic tests such as amniocentesis and chorionic villus sampling .