Hello just thought i would share my story with you as yours sounds similar to mine, i too had a high NT scan of 6.0mm at 12 weeks with nasal bone present. I had a 1:29 for Trisomy 18 and 1:18 Trisomy 13. I had an amnio and all came back normal. I was then sent for a fetal echo cardigram at 20 weeks to check the baby's heart and again all came back normal. At 30 weeks i had another U/S to check the anatomy and they found the fluid from the high NT scan had completely gone. I was told some babies develop slower than others and that my baby was completely normal. I totally understand what your going through but just remember that the NT scan is not a diagnostic test it just tells you the likely hood of chomosonal abnormalities! If the amnio is normal you have gotten over the biggest hurdle.