The Deal

$25 for a 10-minute ultrasound package ($55 value) * 2D ultrasound * Gender determination * Hear the baby’s heartbeat * Eight black-and-white photos * DVD

3D and 4D Ultrasounds: Seeing Babies Like a Bat

Though ultrasound is used as a diagnostic tool today, it was considered a therapy when it first appeared in medicine in the 1920s. Read on to learn how today’s 3D and 4D ultrasounds work.

Ultrasound machines are complex pieces of equipment, but the basic principle is so simple a bat can use it. Send out high-pitched sound signals (so high-pitched humans can’t hear them, in fact), and listen for them to bounce back. The time it takes for the sound to return tells you how close you are to another object, and sending dozens of these signals per second gives you a pretty good picture of the contours of the environment ahead of you and which bugs are juiciest. In the case of an ultrasound machine, these calculations typically map a 2D picture of a growing fetus in the womb. A 3D ultrasound takes this idea a step further, sending ultrasonic waves from a variety of angles around the body to provide a significantly more detailed picture. Adding the element of time results in a moving 3D image, often called a 4D ultrasound. Both 3D and 4D ultrasounds are elective procedures, most commonly used to show what a baby looks like and to identify its gender.

Though ultrasonic technology is used as a diagnostic tool today, it was considered a therapy when it first appeared in medicine in the 1920s, using much more intense ultrasonic energy to apply controlled heat to tissues deep within the body. However, in 1955, Professor Ian Donald of Glasgow University’s Department of Midwifery began to test its application to the diagnosis of tumors, creating a stir in the medical community when he identified a large but operable ovarian cyst in a patient who had been misdiagnosed with inoperable cancer of the stomach. In 1959 he discovered that the ultrasonic waves could provide images of fetuses as well, allowing doctors to study pregnancy at all stages, diagnose any complications, and help name the baby by seeing which celebrity it looks most like.