1. Objective:A few trisomy 21 cells in normal chromosome karyotype was been observed for study of the correlation of clinical phenotype and development damage in sick children of Down's syndrome.

2. Down syndrome (trisomy 21) is a disorder caused by the presence of an extra 21st chromosome.

3. A short femur is associated with trisomy 21 rather than trisomy 13 and holoprosencephaly.

4. If this is a patient with trisomy 21, it become more complicated.

5. Down's syndrome or trisomy 21 occurs in around 1 in 800 births and older women are at higher risk.

6. Our findings also point to the increasing importance of fetal ultrasonography in the prenatal diagnosis of fetal trisomy 21.

7. One of their main findings is the increasing importance of fetal ultrasonography in the prenatal diagnosis of fetal trisomy 21.

8. Results:(1) 80 cases in 1118 pregnant women were screened as high risk for Down's syndrome(/trisomy 21.html), and 1 was verified as trisomy 21 through prenatal diagnosis.

9. There is a weak but fairly convincing association between chromosomal abnormalities such as trisomy 21 (Down syndrome) and echogenic foci in the heart.

10. Relative to fetuses with a nasal bone, those without a nasal bone were estimated to have about 150-times the risk of having trisomy 21.

11. Derivation of a formula for determination of proportion of paternal trisomy 21 is presented.

12. The nasal bone was absent in 43 of 59 (73%) trisomy 21 fetuses and in three of 603 (0.5%) fetuses with normal karyotype.