Last reviewed 01/2018

Triploidy is a chromosomal abnormality with the constitution 69,XXY , or, less commonly, 69,XXX. It occurs in 2% of all conceptions with resulting early spontaneous abortion.

In most cases, the extra set of chromosomes is paternally-derived, either from double fertilisation, or from fertilisation with a double sperm.

Clinically, if the triploid fetus survives to term, the following may present:-

  • low birth weight
  • disproportionately small trunk to head size
  • syndactyly
  • multiple congenital abnormalities
  • large placenta with hydatidiform-like changes

The recurrence risk does not seem to be increased in affected parents.