Common Sex Chromosome Aneuploidies

An isolated prenatal diagnosis of 47,XXX (Triple X), 47,XXY (Klinefelter syndrome), or 47,XYY syndrome is not considered, by itself, a medical indication for termination of pregnancy.

These are sex chromosome aneuploidies with highly variable phenotypes, and many affected individuals have normal life expectancy, normal or near-normal cognitive function, and good quality of life.

Condition Structural Anomalies Intellectual Disability Life Expectancy Fertility
47,XXX Usually absent Usually normal intelligence with increased risk of language/learning difficulties Normal Usually normal
47,XXY Usually absent Usually normal intelligence with language/learning difficulties common Normal or near normal Usually infertile without assisted reproduction
47,XYY Usually absent Usually normal intelligence with increased risk of ADHD, speech/language, or learning difficulties Normal Usually normal

Comparison of Common Sex Chromosome Aneuploidies

Feature Turner (45,X) Triple X (47,XXX) Klinefelter (47,XXY) XYY (47,XYY)
Sex Female Female Male Male
Stature Short Tall Tall Tall
Puberty Delayed/absent without treatment Usually normal Often incomplete due to hypogonadism Normal
Gonadal Function Ovarian failure Usually normal Testicular failure Normal
Fertility Usually infertile Usually normal Usually infertile Usually normal
Hormone Profile ↑FSH, ↑LH, ↓Estrogen Usually normal ↑FSH, ↑LH, ↓Testosterone Usually normal
Common Neurodevelopmental Features Specific learning difficulties Speech/language delays Language and learning difficulties Speech/language delays, ADHD more common