ultrasound

Can you tell from your ultrasound if the baby has down syndrome ? I had to transfer to a different place and I had to get all my records transfered to the new place. I did all my testing the chromosome and down syndrome and I was told the baby was normal and I was low risk but I feel like something not right since I was at my ultrasound since 12 and I just got done right now. had 2 other people come in and do the ultrasound. I forgot what but she said I could do a testing to know for sure if the baby has it or not but in the ultrasound she said she didn't see anything out of the ordinary. I'm 24 weeks. this is not my first I have a 4 year old perfectly healthy