linguistic:translation, structural:summarization
Causes

Most cases of trisomy X occur through maternal nondisjunction, with around 90% of cases traced to errors in oogenesis. The vast majority of cases of trisomy X occur randomly; they have nothing to do with the chromosomes of the parents and little chance of recurring in the family. Nondisjunction is related to advanced maternal age, and trisomy X specifically appears to have a small but significant maternal age effect. In a cohort of women with trisomy X born in the 1960s, the average maternal age was 33. The risk of women with full trisomy X having chromosomally abnormal children is low, likely below 1%. Recurrence may occur if the mother has mosaicism for trisomy X, particularly in ovarian cells, but this makes up a small fraction of cases.