Can amniocentesis confirm NIPT?

Yes. This is exactly what it is for, and ACMG recommends it. After a high-risk NIPT result, ACMG's position is that NIPT is not diagnostic and confirmatory testing — CVS or amniocentesis — is recommended, with the risks of those procedures explained to you. The reason confirmation is needed rather than optional: NIPT analyses DNA from the placenta. The placenta and the baby usually have the same chromosomes, but not always. Confined placental mosaicism, where the abnormality is in the placenta only, is a recognised cause of false-positive NIPT results. Amniocentesis examines cells from the baby itself, so it is not subject to that limitation. Amniocentesis also tells you something NIPT cannot: the mechanism. Down syndrome caused by an extra chromosome, by a translocation, or by mosaicism all look the same on NIPT but carry different recurrence risks for future pregnancies. ACMG specifically notes this as a reason diagnostic testing matters after NIPT. If you decide against an invasive procedure, ACMG recommends that an effort should be made to obtain cord blood after birth so the result can be confirmed then. Ask for this to be arranged in advance rather than remembered on the day. You are also entitled to referral to a genetics professional if your obstetrician is not comfortable counselling you through this.