ABSTRACT
The advent of high-resolution transvaginal ultrasound has revolutionized our understanding of the development of normal early human pregnancy. Knowledge of the ultrasound appearances in normal early pregnancy and a good understanding of the pitfalls, especially in the emergency setting, is essential for the accurate diagnosis and management of early pregnancy problems. The first demonstration of an early intrauterine pregnancy by means of a transvaginal ultrasound scan (TVS) was reported in 1967.1 Since then, dramatic improvements have occurred and the development of high-resolution ultrasound imaging has enabled the anatomy and physiology of the human fetus to be studied in vivo from as early as the 3rd week postimplantation onwards.
