EUROCAT study: Analysis of rare unbalanced chromosome abnormalities

The aim of the study is to establish the Prevalence in Europe of rare chromosomal abnormalities diagnosed prenatally or in infancy. The prevalence of the major trisomies is well established but there are fewer data on the prevalence of rarer chromosome abnormalities for the wider European population. We can consider two types of prevalence: the ?potential prevalence? if all newborns were screened, and the ?diagnosed prevalence? which depends on the level and type of screening in place in each country.  It is this latter that we are interested in and able to address in EUROCAT.

The main analysis would include all unbalanced chromosome errors EXCEPT trisomies 21,18,13, XXX, XYY and XXY and 45,X  to provide an overall prevalence of the rarer chromosome abnormalities but the introduction will include a prevalence of all chromosome abnormalities for a reference basis.

These would be further subdivided into:

• Mosaic trisomies (non-21,18,13, X, Y)
• Autosome deletions including microdeletions*
• Autosome duplications
• Marker chromosomes.