The First Look: Are Ultrasounds Safe And Necessary?

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One of the most exciting moments during pregnancy is when you get to view your developing infant on an ultrasound monitor. That’s the first time you really “see” your baby — the shape of the head, the arms and legs, maybe even a glimpse of the familial nose.

Ultrasound is a common and generally safe procedure. It uses high-frequency sound waves that pass through your body and the baby’s body to create an image. It converts these to a visual image on a monitor, which allows you and your doctor to “see” the baby inside your uterus.

Most pregnant women will undergo at least one ultrasound, usually somewhere between 16 and 20 weeks of gestation.

Since fetal ultrasound first came into widespread use in the U.S. in the 1970s, the technology has improved to the extent that the detail provided is exquisite. But is it always necessary? And is it safe?

Even in low-risk pregnancies, ultrasound is useful for monitoring fetal health and growth, and is the most accurate technology available to confirm your due date. If there are any concerns that your baby may be at risk, ultrasound can help provide the information your doctor needs to give you the best possible prenatal care.

Charles Hageman, MD, obstetrician/gynecologist, emphasizes the benefits and safety of fetal ultrasound.

Click play to watch the video or read video transcript.

Most pregnant women will undergo at least one ultrasound, usually somewhere between 16 and 20 weeks of gestation. Ultrasounds may be done at various times for different reasons.

In the first trimester

  • To establish the due date
  • To determine the number of fetuses and identify placental structures
  • To diagnose an ectopic pregnancy or miscarriage
  • To examine the uterus and other pelvic anatomy
  • In some cases, to detect fetal abnormalities

Mid-trimester (sometimes called the 18- to 20-week scan) 

  • To confirm the due date (although a due date set in the first trimester is rarely changed)
  • To determine the number of fetuses and examine the placental structures
  • To assist in prenatal tests, such as an amniocentesis
  • To examine the fetal anatomy for abnormalities
  • To check the amount of amniotic fluid
  • To examine blood flow patterns
  • To observe fetal behavior and activity
  • To examine the placenta
  • To measure the length of the cervix
  • To monitor fetal growth

Third trimester 

  • To monitor fetal growth
  • To check the amount of amniotic fluid
  • As part of a biophysical profile (usually combined with fetal heart rate monitoring)
  • To determine the position of a fetus
  • To assess the placenta

How Is an Ultrasound Scan Done

Generally, there are two ways to perform an ultrasound during pregnancy.

Abdominal ultrasound 

In an abdominal ultrasound, gel is applied to the abdomen. The technician or doctor glides a hand-held ultrasound transducer over the gel to create the image. For an abdominal ultrasound, you may be asked to drink liquids so you have a full bladder. This may cause temporary discomfort, but gives a “landmark” to locate your uterus. It also helps make the image clearer.

Transvaginal ultrasound 

In a transvaginal ultrasound, a small transducer (covered with a condom or other sterile latex shield) is inserted into the vagina and rests against the back of the vagina to create an image. An empty bladder is required.

A transvaginal ultrasound produces a sharper image and is often used in early pregnancy. You should have little discomfort from this procedure. It usually takes less than half an hour to complete.

What Types Of Ultrasound Are Available?

2-dimensional, or 2-D: The most common ultrasound imaging technique is two-dimensional, or 2-D. This gives a flat picture of one aspect of the image.

3-D: If more information is needed, a 3-dimensional ultrasound exam can be done. This technique requires a special machine and special training. But the 3-D image allows your doctor to see width, height and depth of images, which can be helpful in diagnosis.

4-D: The latest technology is 4-D ultrasound, which allows the doctor to see the unborn baby moving in real-time. With 4-D imaging, a 3-dimensional image is continuously updated, providing a "live action" view. These images often have a golden color, which helps show shadows and highlights.

What Are the Risks And Benefits?

Fetal ultrasound has no known risks other than mild discomfort due to pressure from the transducer on the abdomen or in the vagina. No radiation is used.

Transvaginal ultrasound requires covering the ultrasound transducer in a plastic or latex sheath, which may cause a reaction in women with a latex allergy.

What About “Keepsake” Ultrasounds?

Fetal ultrasound is sometimes offered in nonmedical settings to provide keepsake images or videos for parents. Ultrasound is considered safe only when performed by trained personnel; untrained personnel may give parents false assurances about their baby's well-being, or an abnormality may be missed. “We recommend that you have your ultrasound done by trained medical personnel who can correctly interpret findings,” advises Dr. Hageman.

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