Ultrasound is an essential tool for the evaluation of early pregnancy structures. The main method used during early pregnancy is transvaginal ultrasonography, in order to evaluate the course of the pregnancy during the first weeks. Although our knowledge on ultrasound has increased significantly during the last few years, still early pregnancy remains an area with not so well understood findings and structures. In this article, we will review the timeline of the first visualization of the most significant figures, which are expected to be present throughout the first trimester in a normally developing pregnancy. In addition, the suspicious and the diagnostic ultrasound findings of early pregnancy failure will be presented. We will highlight that the diagnosis of early pregnancy failure must be set by following the cutoff values which are established in order to eliminate the possibility of a false positive diagnosis and to avoid any harmful intervention in a viable pregnancy. Finally, we will denote the prognostic predictive value of evaluation of fetal heart rate and subchorionic hematomas presence in early pregnancy. Aim of this article is to review the literature regarding the diagnosis and prognosis of early pregnancies, improve clinicians’ knowledge on this issue, and of course to help avoid or decrease possible misdiagnosis.