Human body is made up of cells within which structures known as nucleus exist. Nucleus contains 46 chromosomes and any deficiency or a surplus in the number of these chromosomes causes chromosomal diseases to appear. Similar to the body’s cells, there are 46 chromosomes in immature egg cells.
When a girl is born, a certain number of egg cells in the ovaries is present although it varies from person to person. After the age of 12-one of these egg cells matures each month. If this mature egg is fertilized by a sperm, then pregnancy occurs. If no fertilization is formed, egg will be aborted. Unlike sperm cells, egg cells are not constantly renewed ones.
The fundamental process as the egg cells are formed, the number of chromosomes must be halved ultimately giving rise to 23 chromosomes and this cell division cycle continues many years for women. This cycle somehow might be disrupted due to certain reasons which causes a chromosomal disease, Down’s Syndrome.
One of the foremost factors affecting egg cell maturation period is known as advanced maternal age. Scientific studies have shown that the probability for the egg cells formed after 35 years of age, the probability of fault in maturation mechanism of egg cells is significantly high. Because of this fact, frequency of chromosomal abnormalities is remarkably high for those who become pregnant after 35.
Therefore, advanced maternal age pregnancies may end up with chromosomal disorders such as Down Syndrome (trisomy 21) which is the most commonly observed genetic disease in late pregnancies. Although normal incidence for Down Syndrome is in between 1/700 to 1/800(less than 0,1%), this ratio rises up to 1-4% for 40-45 years old pregnants. On account of such a high risk of having a baby with Down Syndrome, advanced age mother candidates should be informed about chromosomal diseases and prenatal diagnosis should be suggested.