The advent of color Doppler, power Doppler and, more recently, three-dimensional imaging has very dramatically developed into a revolution of new ways of doing and seeing things. These developments now occur at such a rapid pace that unless we keep up with the developing technology, we will inevitably and inexorably fall behind. In order to stay with the leading edge of diagnostic ultrasound, one has to keep pace with what colleagues are doing around the world. This book, written by the lecturers of the Ian Donald Inter-University School of Medical Ultrasound, represents the current knowledge on one of the newest achievements in obstetric and gynecologic ultrasonography, transvaginal sonography.