This chapter systematically examines ultrasound protocols for first-trimester pregnancy evaluation, encompassing both physiological development and pathological conditions. Core assessments include gestational sac localization, yolk sac verification, and embryonic cardiac activity detection to confirm early pregnancy viability. Miscarriage subtypes—threatened, incomplete, and missed abortion—are differentiated through serial monitoring of embryonic growth parameters and decidual reaction patterns. Ectopic pregnancy diagnosis prioritizes identification of extrauterine gestational sacs with embryonic structures, supported by Doppler evaluation of peri-implantation vascularity and differentiation from pseudogestational sacs. The evaluation of multifetal pregnancies prioritizes early determination of chorionicity and amnionicity, establishing a diagnostic foundation for risk-stratified surveillance protocols and complication prevention strategies. Special considerations address assisted reproduction pregnancies, focusing on gestational dating adjustments for embryo transfer timelines. Through standardized imaging criteria and risk-stratified management algorithms, this framework enables early detection of nonviable pregnancies, guides intervention timing (expectant vs. surgical management), and optimizes counseling for high-risk cases.