Why karyotype cystic hygroma cells?

This publication has 2 references indexed in Scilit:

• Fetal karyotype from cystic hygroma fluid: Diploid/tetraploid mosaicism
  Prenatal Diagnosis, 1993
• Proposed guidelines for diagnosis of chromosome mosaicism in amniocytes based on data derived from chromosome mosaicism and pseudomosaicism studies
  Prenatal Diagnosis, 1992