Prenatal Ultrasound

Your Guide to a Healthy Pregnancy

What is ultrasonography?

During ultrasonography, or ultrasound, high frequency sound waves, inaudible to the human ear, are transmitted through your abdomen via a device called a transducer.  The echoes are recorded and transformed into video or photographic images of your baby.  The ultrasound can be used during pregnancy to show images of the amniotic sac, placenta and ovaries.

The idea for ultrasonography came from sonar technology, which makes use of sound waves to detect underwater objects.  Ultrasound might be used with other diagnostic procedures, such as amniocentesis, or by itself.

Transvaginal ultrasound

Most prenatal ultrasound procedures are performed topically, or on the surface of the skin, using a gel as a conductive medium to aid the quality of the image.  However, a transvaginal ultrasound is performed using a tubular probe that is inserted into the vaginal canal.  This method of ultrasound produces an image quality that is greatly enhanced.

A transvaginal ultrasound is not a common prenatal procedure.  However, it might be used early in pregnancy to get a clearer view of the uterus or ovaries if a problem is suspected.  It might also be used early in pregnancy to determine how far along you are in your pregnancy (gestational age) if the is uncertain or unknown.

Are there any side effects?

Studies have shown ultrasound is not hazardous.  There are no harmful side effects to you or your baby.  In addition, ultrasound does not use radiation, as do X-ray tests.

When is an ultrasound performed during pregnancy?

An ultrasound is generally performed for all pregnant women between 18 and 22 weeks gestation (anatomy scan).  During this ultrasound, the doctor will confirm that the placenta is healthy and attached normally, and that your baby is growing properly in your uterus.  The baby’s heartbeat and movement of its body, arms and legs can also be seen on the ultrasound.  If you wish to know the gender of your baby, it can usually be determined during the anatomy scan.  Be sure to tell the ultrasound tech whether or not you want to know the gender of your baby.  Please understand that ultrasound is not a fool-proof method of determining your baby’s gender.  There is a chance that the ultrasound images can be misinterpreted.

An ultrasound is performed earlier in pregnancy to determine:

  • Gestational age
  • Presence of more than one fetus
  • Nuchal translucency

Later in pregnancy, an ultrasound might be used to determine:

  • Fetal well-being
  • Placenta location
  • Amount of amniotic fluid around the baby
  • Position of the baby
  • Baby’s expected weight

Major anatomical abnormalities or birth defects can show up on ultrasound.  Even though ultrasound is safe for mother and baby, it is a test that should be done only when medically necessary.  If you have an ultrasound that is not medically necessary (for example, to simply see the baby or find out the baby’s sex), your insurance company might not pay for the ultrasound.