Question
What are the cutoff risks for Down syndrome screening?
Answer
Down syndrome screening primarily involves testing specific proteins and hormone levels in pregnant women’s serum to assess the risk of their fetus having Down syndrome. The results are typically expressed as a risk ratio, and if this ratio exceeds a certain cutoff value, it is classified as high risk. The definition of high risk may vary depending on the screening method, region, and healthcare facility, usually between 1 in 270 to 1 in 1000. If the screening result indicates a higher risk, further diagnostic tests such as amniocentesis or non-invasive prenatal genetic testing may be needed to confirm whether the fetus actually has Down syndrome or other chromosomal abnormalities.