The umbrella term Fetal Alcohol Spectrum Disorders (FASD) brings together under its definition a heterogeneous continuum of disabilities linked by a common etiology and pathogenesis: exposure to alcohol during intrauterine life. Despite extensive research, definitive toxic thresholds remain elusive, underscoring the recommendation for complete alcohol abstinence during pregnancy and lactation. FASD poses diagnostic challenges due to its varied presentations and heterogeneous phenotype. Consequently, no singular diagnostic guideline exists, with multiple expert-driven diagnostic systems globally available. This review aims to synthesize recent and notable guidelines facilitating FASD diagnosis. While efforts were made to include the latest diagnostic systems, determining which scheme is best applied to each individual patient population necessitates clinician discretion. In Italy, the guidelines proposed by Hoyme, revised in 2016, are commonly utilized, yet comparative analysis among guidelines offers valuable insights into their historical context and diagnostic utility. Our discussion explores both similarities and discrepancies among systems for diagnosing FASD, shedding light on their evolution and practical application. The objective of our work was to compare in a practical and precise manner the various existing guidelines used globally regarding the diagnosis of FAS. Our review therefore proposes the diagnostic criteria used by the various working groups and compares them, trying to create a practical comparison between the various guidelines, identifying differences and similarities.