Fetal symptoms of chromosomal abnormalities?

summary

The chromosome in organism is the basic material of nucleus and the carrier of gene. Chromosomal abnormalities can also be called chromosomal dysplasia. Since the International Conference on chromosome nomenclature in Paris in 1971, more than 3000 species of human chromosomal abnormalities and structural aberrations have been found. At present, more than 100 species of chromosomal diseases have been confirmed. Mental retardation and growth retardation are the common characteristics of chromosomal diseases. What exactly causes chromosomal abnormalities and changes in metabolism need further scientific research. Fetal symptoms of chromosomal abnormalities? Let's talk about it

Fetal symptoms of chromosomal abnormalities?

Trisomy, partial trisomy (due to translocation of partial long arm or short arm), and deletion of different chromosomes can form many clinical syndromes. Here are only a few types of clinical common.

The incidence rate of incidence of this disease is about 1/800 in live birth, but the incidence rate of pregnant women in different ages is significantly different: the maternal age is less than 20 years old, and the incidence rate is 1/2000. The age of pregnant women is over 40 years old, and the incidence rate is increased to about 1/40 (table 247-1). About 20% of trisomy 21 babies are born to mothers over 35 years old. Trisomy 21 syndrome can be caused by karyotype, trisomy 21, translocation and chimerism.

When two different cell types exist in the same individual, they are called chimeras. The chimerism of trisomy 21 syndrome may be caused by the absence of chromosome segregation in the embryonic stage. There are two cell lines in most cases, one is normal chromosome and the other has 47 chromosomes. The relative proportion of each cell line can be different between different individuals or in different tissues and organs of the same individual. The intelligence of patients is related to the proportion of trisomy cells in the brain. A few individuals with chimeric trisomy 21 have normal intelligence and almost no clinical symptoms. The incidence rate of chimeric disease in 21 trisomy syndrome is not clear. If the parental germ cells have 21 trisomy chimeras, the chances of producing second children will be greatly increased.

matters needing attention

There are also many types of chromosomal abnormalities that can be expressed as familial tendency, which indicates that chromosomal aberrations are directly related to heredity. Therefore, heredity is an important factor of chromosomal abnormalities.