Functional

When structural or neurological impairments are not observed, all four diagnostic systems allow CNS damage due to prenatal alcohol exposure to be bumessed in terms of functional impairments.[11][24][13][15] Functional impairments are deficits, problems, delays, or abnormalities due to prenatal alcohol exposure (rather than hereditary causes or postnatal insults) in observable and measurable domains related to daily functioning, often referred to as developmental disabilities. There is no consensus on a specific pattern of functional impairments due to prenatal alcohol exposure[24] and only CDC guidelines label developmental delays as such,[11] so criteria vary somewhat across diagnostic systems.

The four diagnostic systems list various CNS domains that can qualify for functional impairment that can determine an FAS diagnosis:

* Evidence of a complex pattern of behavior or cognitive abnormalities inconsistent with developmental level in the following CNS domains — sufficient for a PFAS or ARND diagnosis using IOM guidelines[24]

o Learning disabilities, academic achievement, impulse control, social perception, communication, abstraction, math skills, memory, attention, judgment

* Performance at two or more standard deviations on standardized testing in three or more of the following CNS domains — sufficient for an FAS, PFAS or static encephalopathy diagnosis using 4-Digit Diagnostic Code[13]

o Executive functioning, memory, cognition, social/adaptive skills, academic achievement, language, motor skills, attention, activity level

* General cognitive deficits (e.g., IQ) at or below the 3rd percentile on standardized testing — sufficient for an FAS diagnosis using CDC guidelines[11]

* Performance at or below the 16th percentile on standardized testing in three or more of the following CNS domains — sufficient for an FAS diagnosis using CDC guidelines[11]

o Cognition, executive functioning, motor functioning, attention and hyperactive problems, social skills, sensory problems, social communication, memory, difficulties responding to common parenting practices

* Performance at two or more standard deviations on standardized testing in three or more of the following CNS domains — sufficient for an FAS diagnosis using Canadian guidelines

o Cognition, communication, academic achievement, memory, executive functioning, adaptive behavior, social skills, social communication