A 3-year-old girl with a history of prenatal exposure to methamphetamines is brought to the PMHNP by her grandmother for an evaluation of her readiness to attend preschool. She demonstrates substantial delays across multiple domains of functioning, including communication, learning, attention, and motor development. These deficits will limit her ability to interact with same-age peers. She also requires substantial support in all activities of daily living at home. Due to custodial circumstances, her grandmother is a poor historian and is unable to provide information about the age of onset for these symptoms. What is the most appropriate diagnosis?

Choice A reason: Autism spectrum disorder is primarily characterized by social communication deficits and restricted/repetitive behaviors, not global delays across all domains. Choice B reason: Global developmental delay is used for children under 5 when significant delays are present in multiple developmental domains and the age of onset is unclear, making this the most appropriate diagnosis. Choice C reason: Major neurocognitive disorder is diagnosed in older individuals with acquired cognitive decline, not in young children with developmental delays. Choice D reason: Intellectual disability requires evidence of deficits that emerged during the developmental period, but if the age of onset cannot be determined, global developmental delay is preferred for children under 5.