- 92 XXYY or 92 XXXX
- Rare (5-6% of chromosomal
abnormalities).
- May be observed in molar
pregnancies, but the mechanism for the origin of the extra chromosomes
seems different.
- Tetraploid cells are
frequently found in amniotic fluid (not considered as representing the
fetal karyotype), but tetraploidy is rarely reported in liveborn infants.
Prenatal diagnosis is therefore difficult requiring both cordocentesis and
analysis of fetal blood lymphocytes.
- Usually cannot be diagnosed
prior to 24 weeks gestation.
Link
to Pathophysiology
Link
to Ultrasound