What are some characteristics that a doctor can see on u/s that will give a thought of the baby having down's?

Answer 1

since downs syndrome is a genetic defect of the 21st chromosome aka Trisomy 21 the obvious signs show up in a blood test also ultrasound and on yourself if you are over 35-40 and this is a first child do you have the characteristic epicantlic slit (slanted eyes ) also higher eyebrows and forehead and does it run in the family have you been smoking , taking drugs , exposed to radiation , chemicals, pesticides, herbacides and in what shape are you in physically, nutritionally, and emotionally relax babies that have downs syndrome are the nicest seeetest babies in the world even as the grow up they have no concept of good and evil all people are good and they are so loving and nice and easily trainable if you have patience and a sense of humor best wishes hope this helps gorbalizer

Answer 2

pretty sure that can only with detectect with an amniocentesis. basically they have to get a sample of your amniotic fluid to test it.
That is definitely the earliest way to find out. I don't know if there are characteristics that develop later in pregnancy that they could tell bu that.