Ultrasound in Pregnancy: An Overview

November 21, 2009

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Ultrasound in Pregnancy: An Overview

by Marjorie Greenfield, M.D.
reviewed and revised by Marjorie Greenfield, M.D.

The first obstetrical use of ultrasound was in 1958. Over the past 25 years, ultrasound has become almost routine in the care of pregnant women. Ultrasound is a method of creating an image by "bouncing" sound waves off tissues. The current technology uses "real time" ultrasound, meaning that you see the picture on a screen as it is obtained. These images can also be recorded digitally, on videotape, or in still photos.

Safety
Ultrasound in its current form seems to be completely safe for the fetus. No risks have been demonstrated in its 25 years of common use.

Having an ultrasound
Obstetrical ultrasound can be performed trans-abdominally (TA-US) or trans-vaginally (TV-US).

Trans-abdominal ultrasound: TA-US is most useful in the second and third trimester. For a trans-abdominal ultrasound, the technician puts a gel on your abdomen (to transmit the sound waves) and moves the transducer (which looks like a microphone), over your uterus to create images of the fetus. You may be able to look at the screen and see moving (in both meanings of the word) pictures of your baby.

Trans-vaginal ultrasound: Trans-vaginal ultrasound is used most commonly in the first trimester, and sometimes as an adjunct to trans-abdominal scanning later on in the pregnancy. The TV-US transducer is shaped like a long narrow probe, covered with a condom for sterility, and placed in your vagina. Gel is placed into the condom for transmission of sound waves, and onto its outer surface for lubrication. TV-US feels a lot like having a Pap test.

Neither type of ultrasound should be painful, although sometimes the TA-US requires a full bladder, which can be uncomfortable.

Who needs ultrasound?
This is a question that is being hotly debated: should ultrasound be routine, or used only if there are questions or problems with the pregnancy? While there isn't any research that has shown that babies do better with routine ultrasound, many practitioners (and many parents) still feel most comfortable if they have "seen" the fetus before birth. Routine ultrasound is believed to be safe, but there is a financial cost to ultrasound that may prevent it from being used on a routine basis.

Reasons for having an ultrasound

If the due date is unclear
If there is vaginal bleeding or severe abdominal pain
If the uterus seems too big or too small during prenatal visits
If there is great risk of poor fetal growth or if growth can't be assessed adequately (as in twins or maternal obesity)
If there is an increased likelihood of birth defects
In any situation where getting an image of the baby, placenta, uterus or cervix will clearly assist in the care of the mother and baby


RELATED INFORMATION

			Amniocentesis for Second Trimester Diagnosis
			Triple Check or Quad Screen Testing in Pregnancy
			Moms-to-Be Testing
			Ultrasound in Pregnancy

Created September 10, 2000
Reviewed and revised August 25, 2004

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