Down syndrome is a developmental disorder that results from chromosomal abnormality. It is considered to be the most common genetic cause of intellectual disability, occurring in approximately 1 in 600 live births, making it particularly relevant to consider within the context of abnormal and clinical psychology. Notably, the number of terminated pregnancies following positive prenatal testing for Down syndrome likely attenuates the prevalence rates for the disorder. Although Down syndrome is genetic, it is—for the most part—not hereditary. It occurs randomly across all races, cultures, and levels of socioeconomic status. However, the risk of having a child with Down syndrome does increase with maternal age, and some fairly recent research suggests that paternal age above 42 years increases the risk of having a child with ...