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CAR: Anomalies - Chromosome
Triple X Syndrome

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    Triple X
    YY syndrome


Introduction Antenatal Postnatal West Midlands Data


Triple X syndrome occurs in females as a result of one or more additional X chromosomes. Instead of the usual female karyotype 46XX, the karyotype is 47XXX or more rare 48XXXX or 49XXXXX. Affected females are physically normal

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Except for the severe and rare expression of this syndrome with karyotype 49XXXXX, most cases of triple X syndrome have no distinguishing features on ultrasound.

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Girls with triple X syndrome have a normal phenotype but are taller than average. Puberty and fertility are normal but premature ovarian failure can occur. Educational problems are more common than with other sex chromosome anomalies. Average IQs are lower, there is some impairment of cognitive ability, and development of speech may be delayed. Individuals with karyotypes 48XXXX and 49XXXXX have more severe physical characteristics such as microcephaly, mental retardation, and dysmorphic facial features

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To be added

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© Perinatal Institute 2011