Obstetric ultrasonography



Obstetric sonography (ultrasonography) is the application of medical ultrasonography to obstetrics. Here, ultrasound is used to visualize the embryo or fetus in its mother's uterus (womb). In some countries, routine pregnancy ultrasound scans are performed to detect developmental defects before birth, the perhaps most common method uses a measurement of the nuchal translucency thickness ("NT-test", or "Nuchal Scan") which can predict with high accuracy whether the fetus is affected by the Down syndrome.



The sex of the baby can usually be determined 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, that means care has to be taken in interpreting the accuracy of the scan.



Role of Obstetric Ultrasound in the Development of Diagnostic Ultrasound Technology
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.

Safety issues
Current evidence indicates that diagnostic ultrasound is safe for the unborn child, unlike radiographs, which employ ionizing radiation, although no randomized controlled trials have been undertaken to test the safety of the technology. For this reason the American Institute of Ultrasound in Medicine criticised celebrity actor Tom Cruise in November 2005 after he purchased an ultrasound machine for personal use at home, presumably to image the pregnancy of his partner Katie Holmes.