Ia a ultersund 100 pure cent?

i was 20 weeks prgo whe i went for my 2ed ultersound and every tets thay done was fine until now the ultersound the docs are saying thay cant see the babys bladder r kindenys and he saying the baby might not make it when its born i just cant belive it the baby moves around and the heart rate is 149 the bbay looks good in the ultersound but he saying my amniotic fluid is low to none im going 10-21-08 for a 4th ultersound i pray to Gd thi sdoc can find it please all thi swh red thi splease pray 4 me and my baby im all so in my 30's and God ha sblessed me with 2 wonderful kids i just anted 1 more ty 4 ur help