I see questions about NIPT all the time so I  thought I'd share my little story. I had my harmony test drawn last Tuesday, and got my results today (6 days later). My doctor explained that the trisomy detection is 98-99% and the gender is 99% but it is possible if pregnancies are too close together that a Y chromosome can be picked up from the previous fetus (but it's very rare). I'm no professional...only sharing the info I was given and I hope it helps answer some questions!!