Question
How is normalcy determined in Down syndrome screening?
Answer
The normal range for Down syndrome screening is typically determined by a cutoff value of 1 in 275, with any risk level above this cutoff considered high risk. For the general population under the age of 37, the likelihood of having a baby with Down syndrome is approximately 1 in 750. Down syndrome, also known as trisomy 21, is a common chromosomal abnormality disorder characterized by an extra pair of 21st chromosomes. Down syndrome screening is an economical and simple method to assess the risk of fetal intellectual development. If the screening result shows a high risk, it is recommended to undergo further amniocentesis for confirmation. Down syndrome screening primarily targets trisomy 21, trisomy 18, and neural tube defects to evaluate the likelihood of these abnormalities.