Rapid Aneuploidy Testing, Traditional Karyotyping, or Both, in Prenatal Diagnosis

HKJGOM 2005; 5 (1) 33 Introduction The most frequent foetal chromosomal abnormalities involve the autosomes 21, 18, 13 and sex chromosomes X and Y. Aneuploidy or alterations in copy number of these chromosomes, including Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), Trisomy 13 (Patau syndrome), 45,X (Turner syndrome), 47,XXY (Klinefelter syndrome) and Triploidy (presence of 3 copies of each chromosome), account for more than 80% of clinically significant chromosomal abnormalities diagnosed in the prenatal period. Down syndrome is a well-recognised cause of mental retardation, cardiac and other congenital abnormalities. Edwards syndrome and Patau syndrome lead to multiple congenital abnormalities and early neonatal death. The phenotype of Turner syndrome is highly variable including short stature, amenorrhoea, infertility, cardiac and renal malformations. Klinefelter syndrome is associated with a relatively mild phenotype. Foetuses with triploidy are severely growth retarded and usually die in-utero.