for the National Geographic Channel
and National Geographic News
The new generation of three- and four-dimensional ultrasound imagery provides striking views of fetuses inside the womb. Parents-to-be appreciate the lifelike pictures, and doctors gain an improved understanding of fetal development and behavior.
"It's almost a new science, in a way. It's taught us so much about how the fetus develops at an early stage," said Professor Stuart Campbell of the Create Health Clinic in London. Campbell, one of the world's leading experts in obstetrics, has been working with ultrasound technology since its earliest days and with so-called four-dimensional images since their debut about four years ago.
Four-dimensional imagery shows objects in 3-D moving in something close to real time. Doctors have long known that fetuses move, but the physical behavior revealed by 4-D scans is expanding that knowledge exponentially.
"We see the earliest movements at 8 weeks," Campbell said. "By 12 weeks or so they are seen yawning and performing individual finger movements that are often more complex than you'll see in a newborn," he said. "It may be due to the effects of gravity after birth."
The images reveal facial expressions, like smiling, at 20 weeks. Beyond 24 weeks fetuses may suck their thumbs, stick their tongues out (perhaps using newly developed taste buds to sample amniotic fluid imbued with the flavors of the mother's food), and make apparently emotional faces.
Many of the reflexes seem designed to help the fetus with tasks it will need after birth, such as opening its eyes and sucking.
Campbell believes that ever improving imageryparticularly the 4-D scans, which are inching ever closer to displaying real-time movementrepresents the tip of the iceberg for fetal-behavior study.
"I think we ought to study the behavior of the fetus prenatally," he said. "For example, we don't understand why cerebral palsy occurs in 90 percent of the cases it does, but we believe it occurs in the uterus. I think the future lies in first-trimester diagnosis. I can see diagnosing abnormalities in the first 12 weeks."
Computer Advances Drive Improving Imagery
Ultrasound images are made by sending high-frequency sound waves into the mother's body, where they penetrate fluids but bounce back off solids. The rebounding waves are collected to produce an image, traditionally seen as a two-dimensional "slice."
"As computers have gotten faster it's possible for them to process many 2-D slices over a very short period of time and then stitch them together. That's how we got from 2-D to 3-D," said Carol Benson, a radiologist specializing in ultrasound at Brigham and Women's Hospital in Boston, Massachusetts.
"With the 4-D, processing is fast enough that you can watch [movement] as it happens. When it gets faster it will eventually appear to be in real time."
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