The study was included one thousand and one hundred cases - refereed as DS- from different regions and discretes all over Egypt from January 1996 to October 2003. For all cases routine G- banding cytogenetic analysis was done and extended mosaic study was performed when indicated. Cases confirmed to be DS were then classified into two groups according to the time of diagnosis: prenatal and postnatal diagnosed cases.

Results:

The study was included 1100 cases, 93.64 % (1030 cases) were confirmed to have DS by cytogenetic analysis and 67 cases confirmed to have normal karyotype and 3 cases had abnormal karyotype, table (1).

Number ... karyotype

1030 ... Down syndrome

67 ... 46, XX or 46, XY

1 ... 46, X, I (Xq)/ 45, X

1 ... 46, XX, add (15) (q 26)

1 ... 46, XY, add (3)(p 25)

Table (1): karyotype of the referred cases.

Cases confirmed to be DS then classified into two groups according to the time of diagnosis: prenatal and postnatal diagnosed cases. Most of them (98.43 %) were diagnosed postnatally and only 1.56 % were detected prenatally (among 1022 cases of amniocentesis referred for advanced maternal age, previous history of DS or positive prenatal screening test), while 0.01 % were products of conception. The ages of postnatal cases ranged from one hour to 30 years with a mean of 351 days. Diagnosis in the neonatal period was done in 37.7 % of cases, 69.7 % were diagnosed in the first 6 months and 83.9 % were diagnosed in the first year of life.