Can NIPT detect Down syndrome?

Yes — Down syndrome, or trisomy 21, is the condition NIPT detects best. It is the main reason the test exists. But "detect" is the wrong word, and the distinction matters. NIPT screens for Down syndrome. It estimates whether the chance is increased or decreased. It cannot tell you whether your baby has it. A high-risk result means the chance is raised, not that the condition is present. How likely it is to be correct — the positive predictive value — depends on your age and on how common the condition is in women your age. For younger women in particular, a substantial proportion of high-risk results turn out to be unaffected pregnancies. Ask for the positive predictive value for your specific result at your age, rather than the general accuracy figure. Confirming it requires a diagnostic test — CVS or amniocentesis — which examines the baby's chromosomes directly. ACMG recommends this after a positive screen. One further point worth knowing. NIPT cannot tell you the mechanism. Down syndrome caused by an extra chromosome, by a translocation, or by mosaicism all look the same on NIPT, and they carry different recurrence risks for future pregnancies. Only a diagnostic test can distinguish them. If you receive a high-risk result, ask for referral to a genetics professional. You are entitled to balanced information about what Down syndrome actually means today, including the range of outcomes rather than only the difficulties.