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A pregnancy ultrasound is an imaging test that uses sound waves to see how a baby is developing in the womb. It is also used to check the female pelvic organs during pregnancy.
Pregnancy sonogram; Obstetric ultrasonography; Obstetric sonogram; Ultrasound - pregnancy
You will lie down for the procedure. The person performing the test places a clear, water-based gel on your belly and pelvis area and then moves a hand-held probe over the area. The gel helps the probe transmit sound waves. These waves bounce off the body structures, including the developing baby, to create a picture on the ultrasound machine.
In some cases, a pregnancy ultrasound may be done by placing the probe into the vagina. For information on this procedure, see transvaginal ultrasound.
A full bladder is necessary to get a good picture. Therefore, you may be asked to drink 2 to 3 glasses of liquid an hour before the test. You should not urinate before the procedure.
There may be some discomfort from pressure on the full bladder. The conducting gel may feel slightly cold and wet. You will not feel the ultrasound waves.
Some doctors order an ultrasound when they think there may be a problem with the pregnancy or if there is a question about how far along the pregnancy is. Others advocate screening ultrasounds. You should consult your health care provider to determine the most appropriate scanning schedule for you.
A pregnancy ultrasound may be done in the first trimester to:
A pregnancy ultrasound may also be done in the second and third trimesters to:
Some centers are now performing a pregnancy ultrasound around 9 - 13 weeks of pregnancy to look for signs of Down syndrome or other developmental problems in the developing baby. This test is often combined with blood tests to improve the accuracy of results.
The total number of scans will depend on whether a previous scan or blood test has detected problems that require follow-up testing.
The developing baby, placenta, amniotic fluid, and surrounding structures are normal in appearance and appropriate for the gestational age.
Note: Normal results may vary slightly. Talk to your doctor about the meaning of your specific test results.
Abnormal ultrasound results may be due to some of the following conditions:
Current ultrasound techniques appear to be safe, and there is no documented risk to women or their developing babies. Ultrasound does not involve radiation, such as that used when taking an x-ray.
Richards DS. Ultrasound for pregnancy dating, growth, and the diagnosis of fetal malformations. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 9.
Taval VS, Glass CM. Emergency ultrasound. In: Marx JA, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 197.