Obstetric ultrasonography
From Wikipedia, the free encyclopedia
Obstetric sonography (ultrasonography) is the application of medical ultrasonography to obstetrics, in which ultrasound is used to visualize the embryo or fetus in its mother's uterus (womb). The procedure is often a standard part of prenatal care, as it yields a variety of information regarding the health of the mother and of the fetus, as well as regarding the progress of the pregnancy.
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[edit] Fetal Sex Determination
The sex of the baby can usually be determined by ultrasound at any time after 16 weeks, often at the dating scan around 20 weeks into the pregnancy depending upon the quality of the sonographic machine and skill of the operator. This is also the best time to have an ultrasound done as most infants are the same size at this stage of development. Depending on the skill of the sonographer, ultrasound may suffer from a high rate of false negatives and false positives. This means care has to be taken in interpreting the accuracy of the scan.
[edit] Abnormality Screening
In some countries, routine pregnancy ultrasound scans are performed to detect developmental defects before birth. This includes checking the status of the limbs and vital organs, as well as (sometimes) specific tests for abnormalities. Some abnormalities detected by ultrasound can be addressed by medical treatment in utero or by perinatal care, though indications of other abnormalities can lead to a decision regarding abortion.
Perhaps the most common such test uses a measurement of the nuchal translucency thickness ("NT-test", or "Nuchal Scan"). Although 91% of fetuses affected by Down syndrome exhibit this defect, 5% of fetuses flagged by the test are in fact normal.
[edit] Role in Technology Advancement
Obstetric ultrasound has played a significant role in the development of diagnostic ultrasound technology in general. Much of the technological advances in diagnostic ultrasound technology are due to the drive to create better obstetric ultrasound equipment. Acuson Corporation's pioneering work on the development of Coherent Image Formation helped shape the development of diagnostic ultrasound equipment as a whole.
[edit] Safety issues
Current evidence indicates that diagnostic ultrasound is safe for the unborn child, unlike radiographs, which employ ionizing radiation. However, no randomized controlled trials have been undertaken to test the safety of the technology, and thus ultrasound procedures are generally not done repeatedly unless medically called for.
In November 2005, actor Tom Cruise purchased an ultrasound machine for personal use at home, presumably to image the pregnancy of his wife Katie Holmes. For the reasons given above, this action received some criticism in the press from groups including the American Institute of Ultrasound in Medicine.
August 2006: A new study on rodent fetus brains that are exposed to ultrasound showed signs of damage. Speculation on human fetuses can be in a range of no significant complications to variety of mental and brain disorder. The study shows that rodent brain cells failed to grow to their proper position and remained scattered in incorrect parts of the brain.
[edit] External links
- RadiologyInfo: Obstetric Ultrasound Imaging
- A comprehensive guide to Obstetric Ultrasound
- Nuchal Translucency test information page
- 3D Ultrasound Info - Includes sample images and studies
- FDA statement on Fetal Keepsake Videos
- AIUM statement on prudent use of Ultrasound
[edit] References
- "AIUM discourages the sale and use of ultrasound equipment for personal use in the home" Category: MRI/PET/Ultrasound News, Medical News Today, 30 NOV 2005
