cytogenetics
Last reviewed 01/2018
Complete hydatidiform moles typically have a 46 XX karyotype but with both X chromosomes derived from the father. The female pronucleus of the fertilised egg degenerates and the mole develops by duplication of the male pronucleus. A minority are 46 XY. Very rarely, complete hydatiform moles are associated with a foetus.
Incomplete moles usually have a triploid karyotype, 80% of which are 69 XXY. The remainder are 69 XXX or 69 XYY. Occasionally, mosaic patterns are found. Most incomplete moles are associated with a triploid and defective foetus.