Ultrasound: Sonogram – American Pregnancy Association

Posted: May 16, 2019 at 12:52 am

An ultrasound exam is a procedure that uses high-frequency soundwaves to scan a womans abdomen and pelvic cavity, creating a picture(sonogram) of the baby and placenta. Although the terms ultrasoundand sonogram are technically different, they are used interchangeablyand reference the same exam.

There are basically seven different ultrasound exams, but the basic process is the same.

The different types of procedures include:

Transvaginal Scans Specially designed probe transducersare used inside the vagina to generate sonogram images. Most oftenused during the early stages of pregnancy.

Standard Ultrasound Traditional ultrasound examwhich uses a transducer over the abdomen to generate 2-D images ofthe developing fetus.

Advanced Ultrasound This exam is similar to thestandard ultrasound, but the exam targets a suspected problem anduses more sophisticated equipment.

Doppler Ultrasound This imaging procedure measuresslight changes in the frequency of the ultrasound waves as they bounceoff moving objects, such as blood cells.

3-D Ultrasound Uses specially designed probes andsoftware to generate 3-D images of the developing fetus.

4-D or Dynamic 3-D Ultrasound Uses specially designedscanners to look at the face and movements of the baby prior to delivery.

Fetal Echocardiography Uses ultrasound waves toassess the babys heart anatomy and function. This is used to helpassess suspected congenital heart defects.

The traditional ultrasound procedure involves placing gel on yourabdomen to work as a conductor for the sound waves. Your healthcareprovider uses a transducer to produce sound waves into the uterus.The sound waves bounce off bones and tissue returning back to thetransducer to generate black and white images of the fetus.

Ultrasounds may be performed at any point during pregnancy, and theresults are seen immediately on a monitor during the procedure. Transvaginalscans may be used early in pregnancy to diagnose potential ectopicor molar pregnancies.

There is not a recommended number of ultrasounds that should be performedduring routine prenatal care. Because ultrasound should only be usedwhen medically indicated, many healthy pregnancies will not require an ultrasound. The average number of ultrasounds varies with each healthcareprovider.

Additional ultrasounds might be ordered separately if yourhealthcare provider suspects a complication or problem related toyour pregnancy.

Ultrasounds are diagnostic procedures that detect or aid in the detectionof abnormalities and conditions related to pregnancy. Ultrasoundsare usually combined with other tests, such as tripletests, amniocentesis,or chorionic villus sampling,to validate a diagnosis.

An ultrasound exam may be performedthroughout pregnancy for the following medically-necessary reasons:

First Trimester:

Second Trimester:

Third Trimester:

The ultrasound is a noninvasive procedure which, when used properly,has not demonstrated fetal harm. The long-term effects of repeatedultrasound exposures on the fetus are not fully known. It is recommendedthat ultrasound only be used if medically indicated.

No, itdoes not mean there is a problem. The heartbeat may not be detectedfor reasons that include: tipped uterus, larger abdomen, or inaccuratedating with last menstrual period. Heartbeats are best detected withtransvaginal ultrasounds early in pregnancy.

Concern typically developsif there is no fetal heart activity in an embryo with a crown-rumplength greater than 5mm. If you receive an ultrasound exam after week6, your healthcare provider will begin to be concerned, if there isno gestational sac.

Your healthcare provider will use hormone levels in yourblood, the date of your last menstrual period and, in some cases,results from an ultrasound to generate an estimated gestational age.However, variations in each womans cycle and each pregnancy may hinderthe accuracy of the gestational age calculation.

If your healthcareprovider uses an ultrasound to get an estimated delivery date to basethe timing of your prenatal care, the original estimated gestationalage will not be changed.

If there are any questions regarding gestational age, placenta location,or possible complications then more ultrasounds may be scheduled.Because ultrasound should only be used when medically indicated, manyhealthy pregnancies will not require an ultrasound. The average numberof ultrasounds varies with each healthcare provider.

Your healthcare provider willuse hormone levels in your blood, the date of your last menstrualperiod and, in some cases, results from an ultrasound to generatean expected date of conception. However, many differences in eachwomans cycle may hinder the accuracy of the conception date calculation.

The viability of sperm varies as well, which means intercoursethree to five days prior to ovulation may result in conception. Ultrasounddating of conception is not reliable for determining paternity becausethe ultrasound can be off by at least 5-7 days in early pregnancy.

Youmay have an ultrasound between 18 to 20 weeks to evaluate dates, amultiples pregnancy, placenta location or complications. It may alsobe possible to determine the gender of your baby during this ultrasound.Several factors, such as the stage of pregnancy and position of the fetus,will influence the accuracy of the gender prediction.

To be 100% sureyou will have an anxious wait until the birth!

Ultrasoundsare only necessary if there is a medical concern. As noted above,ultrasounds enable your healthcare provider to evaluate the babyswell being as well as diagnose potential problems. For women withan uncomplicated pregnancy, an ultrasound is not a necessary partof prenatal care.

Last updated: November 3, 2017 at 14:29 pm

Compiled using information from the following sources:

1. Williams Obstetrics Twenty-Second Ed. Cunningham,F. Gary, et al, Ch. 16.

2. American Institute of Ultrasound in Medicine


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Ultrasound: Sonogram - American Pregnancy Association

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