Question
A woman who is 18 weeks pregnant asks about her Down syndrome screening results, which indicate a 1 in 100 risk value for Trisomy 21, classified as high risk.
Answer
A professional physician provides an analysis of the condition, noting that Down syndrome, also known as Trisomy 21, is caused by an extra chromosome 21 in the patient’s body. The Down syndrome screening detects the levels of alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) in the maternal serum, combined with age, weight, and gestational age to calculate the risk value. The critical value is typically set at 1/275. If the screening result shows a high risk, it is recommended to undergo amniocentesis or chorionic villus sampling for confirmation.