Doctors diagnose chromosomal disorders using blood samples. A doctor can also detect such disorders before the infant is born, using cells from the amniocentesis or a sample of the chorionic villus, finger-like projections that make up the placenta, according to the Merck Manual.
Chromosomes are the genetic material responsible for providing information for the growth and operation of the body, explains the March of Dimes. Chromosomal disorders occur when there are changes to the number or structure of the chromosomes. About one in 150 babies has a chromosomal defect at birth.
Although most chromosomal defects do not pass from one generation to the next, it is possible to inherit some of these disorders, according to the Genetics Home Reference. Such changes occur as random events during the formation of the egg or sperm. The gain or loss of one chromosome in a reproductive cell affects each cell in the body.
Chromosomal abnormalities are responsible for more than half of miscarriages in which the baby dies before the 20th week of pregnancy, reports the March of Dimes. If the fetus dies after 20 weeks, doctors classify the death as a stillbirth. Some children born with chromosomal defects suffer birth defects, and others have intellectual disabilities. In some children with chromosomal abnormalities, the condition does not cause any serious problems.