Baby's first picture is usually not a Kodak moment but a grainy black-and-white sonogram. Such images-generated with ultrasound technology that sends harmless sound waves into the mother's womb and measures what bounces back-usually tax the imagination of anxious parents trying to discern a foot, rump, or face. Images produced with new 3-D ultrasound technology, however, are a marked improvement. The system uses a monitor, computer controls, a processing unit, and a handheld transducer probe, which emits and collects sound waves, to render nose, lips, eyes, fingers, and toes in astonishing detail. It's as if someone photographed a clay model of the fetus.

Ultrasound was first used for clinical diagnosis in 1942 by Austrian psychiatrist and neurologist Karl Dussik. By the 1980s, improvements in microprocessor speed had advanced it into the 3-D arena. Kazunori Baba of the University of Tokyo, Japan, devised the first successful 3-D ultrasound system for obstetrics in 1984; it compiled a series of 2-D "slices" into a 3-D sonogram. But it has really been in the last couple of years that inexpensive computer technology has made it possible to acquire, reconstruct, and display 3-D images quickly, says Aaron Fenster, director and scientist at the Robarts Research Institute's Imaging Research Laboratories in London, Ontario.