to similarities and differences across the four diagnostic systems. More than 400 problems, however, can occur with FASD. Growth In terms of FASD, growth deficiency is defined as significantly below average height, weight or both due to prenatal alcohol exposure and can be assessed at any point in the lifespan. Growth measurements must be adjusted for parental height, gestational age (for a premature infant), and other postnatal insults (e.g., poor nutrition), although birth height and weight are the preferred measurements. Deficiencies are documented when height or weight falls at or below the 10th percentile of standardized growth charts appropriate to the population. Prenatal or postnatal presentation of growth deficits can occur, but are most often postnatal. Criteria for FASD are least specific in the Institute of Medicine (IOM) diagnostic system ("low birth weight..., decelerating weight not due to nutrition..., [or] disproportional low weight to height" p. 4 of executive summary), while the CDC use the 10th percentile as a cut-off to determine growth deficiency. The "4-Digit Diagnostic Code" allows for mid-range gradations in growth deficiency (between the 3rd and 10th percentiles) and severe growth deficiency at or below the 3rd percentile. Growth deficiency (at severe, moderate, or mild levels) contributes to diagnoses of FAS and pFAS, but not ARND or static encephalopathy. Growth deficiency is ranked as follows by the "4-Digit Diagnostic Code": Severe: Height and weight at or below the 3rd percentile. Moderate: Either height or weight at or below the 3rd percentile, but not both. Mild: Either height or weight or both between the 3rd and 10th percentiles. None: Height and weight both above the 10th percentile. In the initial studies that discovered FAS, growth deficiency was a requirement for inclusion in the studies; thus, all the original people with FAS had growth deficiency as an artifact of sampling characteristics used to establish criteria for the syndrome. That is, growth deficiency is a key feature of FASD because growth deficiency was a criterion for inclusion in the study that defined FAS. This suggests growth deficiency may be less critical for understanding the disabilities of FASD than the neurobehavioral sequelae to the brain damage. Canadian guidelines updated in 2016 deleted growth as a diagnostic criterion. Facial features Several characteristic craniofacial abnormalities are often visible in individuals with FAS. The presence of FAS facial features indicates brain damage, although brain damage may also exist in their absence. FAS facial features