Antenatal screening options
Screening for chromosomal abnormality has evolved significantly in the past 30 years.
This article examines the range of available antenatal tests, past and present, for those wishing to screen during early pregnancy for chromosomal abnormality.
Down syndrome, the most common human chromosomal abnormality, is caused by the presence of an extra copy of the 21 chromosome — trisomy 21.
There are three genetic subtypes: simple trisomy 21, mosaicism (where only some cells are affected) or an unbalanced translocation in which the extra chromosome 21