Three-dimensional (3D) ultrasound has become globally available since the First World Congress on 3D Ultrasound on September 5-6, 1997 in Mainz, Germany. Today this technique offers a broad spectrum of application options in prenatal and gynecologic diagnosis. It has become a valuable supplementary method to conventional 2D ultrasound and is used by skilled operators to clarify suspicious findings. The different visualization modes provide the operator with amazing 3D images that never can be achieved with 2D ultrasound. However, proper use of 3D ultrasound requires a learning curve, technical understanding, spatial perception and continuous training. This book will motivate doctors and sonographers to integrate this substantial technique as a useful tool in their daily routine.