Down syndrome is a condition in which a baby is born with an extra chromosome. People with Down syndrome have an extra copy of chromosome 21, giving them a total of 47 chromosomes instead of the typical 46. Down syndrome is a lifelong condition that can cause symptoms such as unique physical characteristics, poor muscle tone, delayed development, and a short attention span. Find out what causes Down syndrome to learn more about this chromosomal anomaly.
Every year, about 6,000 new babies are born with Down syndrome (about one case in every 700 births), according to national birth estimates.
Scientists have proven that the cause of Down syndrome is a random error in cell division, called nondisjunction. In a child without Down syndrome, a cell that splits in two places one chromosome into one cell, and another in a different cell.
During nondisjunction, a random error occurs that sends both chromosomes into one cell and none into the other cell. Nondisjunction typically occurs during the formation of an egg or sperm.
Three types of chromosomal changes can cause Down syndrome: complete, mosaic, or translocation trisomy 21.
Complete trisomy 21 means that an extra copy of chromosome 21 appears in every cell. This is the most common. Mosaic trisomy 21 means not every cell is exactly the same. Some cells may contain the extra chromosome 21, while others do not.
Translocation trisomy 21 means only part of an extra copy of the chromosome appears in the cells.
No significant cognitive or physical differences exist between children with complete vs. translocation trisomy 21; however, children with mosaic may have different symptoms depending on how many cells carry the extra chromosome.
The error in cell division that causes Down syndrome is random, with the cause unknown.
No environmental or parental factor has any known scientific connection to the cause of Down syndrome. However, mothers older than 35 are more likely to give birth to children with Down syndrome than those under 35.
How Do Doctors Diagnose Down Syndrome?
Diagnosing Down syndrome is possible before or after the birth of the child. Doctors will use diagnostic tests to diagnose the syndrome after birth, or screening tests to make a diagnosis while the child is still in the womb.
Noninvasive prenatal tests such as MaterniT® 21 PLUS can screen a baby for chromosomal abnormalities, including trisomy 21. This test uses noninvasive methods to test for Down syndrome using the mother’s blood sample, rather than drawing amniotic fluid from around the infant.
It can provide early Down syndrome risk assessment as early as week 10 in your pregnancy.
If you are curious as to whether your child could have Down syndrome or another chromosomal abnormality, speak to your health care provider about MaterniT® 21 PLUS.
Increased risk criteria for Down syndrome, such as advanced maternal age, could contribute to the desire for prenatal DNA testing. This noninvasive prenatal test has a five-day turnaround time from the receipt of the mother’s blood sample in the lab.
Your healthcare provider will receive the results and pass the information onto you during an appointment. You can find out if your child has Down syndrome without the risks of prenatal invasive procedures.