The field of diagnostic ultrasound has witnessed extraordinary advancements in recent years. Innovations such as color Doppler, power Doppler, and the advent of three-dimensional (3D) imaging have revolutionized our approach to visualization and diagnosis. These technologies evolve rapidly, making it essential for practitioners to stay abreast of the latest developments to maintain a competitive edge. This textbook, authored by esteemed lecturers from the Ian Donald Inter-University School of Medical Ultrasound, encapsulates contemporary knowledge in one of the most progressive areas of obstetric and gynecologic ultrasonography—transvaginal sonography. Transvaginal ultrasound has become an indispensable tool for obstetricians and gynecologists, offering unparalleled insights into the female reproductive system. The development and refinement of various transvaginal probes, ranging in frequency from 5.0 to 7.5 MHz, have enabled the acquisition of high-quality two-dimensional (2D) and three-dimensional (3D) images of the uterus, ovaries, and early gestational structures. Despite certain limitations, such as a restricted field of view, the clarity and detail of images obtained via the vaginal fornix are unmatched. One of the most exciting advancements in this field is the integration of color Doppler with transvaginal sonography. This combination allows for the simultaneous visualization of structural and flow information, providing new perspectives on blood flow dynamics within the female pelvis. The insights gained from these dynamic studies are comprehensively illustrated throughout this book.