Ultrasound technology is used in obstetrics to verify the viability of a developing baby, check for normal milestones in development and diagnose certain conditions. Although standard ultrasounds, also called sonograms, are two-dimensional---they produce a flat image with no visible depth and a characteristically muddy-appearing image---newer technologies allow for three- and even four-dimensional visualization. As three-dimensional ultrasounds introduce depth into the picture, allowing the machine to capture a lifelike image, four-dimensional ultrasounds also add in the element of time. As such, with a 4D ultrasound, it's possible to watch real-time fetal movement.
Function
The theory behind ultrasound is quite similar to the way a bat finds its way around in the dark. Very high-pitched sounds emitted by the ultrasound device--or a bat, for the sake of analogy--bounce off structures and return to the machine or the bat's ears. Since all sound travels at the same speed, longer gaps of time between sound transmission and sensation indicate greater distances to the object that reflected the sound. A two-dimensional, or traditional, ultrasound sends sound in only a single direction, so it is limited in its ability to resolve the shape of a structure. Three-dimensional ultrasounds send sound in many directions at once, and four-dimensional ultrasounds do so constantly, producing a high-resolution picture that changes with time.
Benefits
In their book, "What to Expect When You're Expecting," Heidi Murkoff and Sharon Mazel point out that there are legitimate medical purposes for most traditional ultrasounds, including gauging gestational age, determining whether a fetus is developing on schedule and looking for defects. Four-dimensional ultrasounds can serve each of these purposes, but offer the additional benefit of allowing the expectant parents to get a good look at their fetus prior to delivery. Further, while it may be difficult to determine gender with 100 percent accuracy using a traditional ultrasound, 4D machines offer greater resolution and accuracy.
Time Frame
Most initial ultrasounds are done around nine to 12 weeks---these images can determine gestational age, but will not yield exciting pictures of the developing fetus because it's still quite small. Second- and third-trimester ultrasounds are more likely to produce keepsake images, and here, 4D ultrasounds offer a significant advantage over traditional imaging techniques, because the images they produce are recognizably human.
Expert Insight
In his book, "What You Didn't Think To Ask Your Obstetrician," Dr. Raymond Poliakin notes that no studies have yet linked ultrasound to fetal abnormalities. Studies, however, have always used relatively low-power ultrasound. As a result, routine 4D ultrasound of a given fetus results in significantly higher exposure than generally recommended. He notes that while privately owned, boutique ultrasound businesses offer parents the opportunity to observe their fetus in the womb, many physicians do not recommend unnecessary ultrasound.
Considerations
The Food and Drug Administration does not recommend utilizing ultrasound for purely entertainment purposes, including visualization of a fetus in order to produce a keepsake photo. Though some physicians will order 4D ultrasounds to get a better view of a fetus in the event that they become concerned about a potential pregnancy complication, most women will not require anything more than a few standard ultrasounds during pregnancy.
References
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- "What You Didn't Think to Ask Your Obstetrician"; Raymond Poliakin, M.D.; 2007
Member Comments