What is the outcome of most pregnancies diagnosed with t-16 m through amniocentesis if iugr and heart defects are already present.?

Consult specialist. If you mean trisomy 18, unfortunately the outcome is not good. You must consult a specialist in "maternal fetal medicine" for a detailed answer. Regardless, if heart defects and iugr are already present, consulting with a specialist in maternal fetal medicine is a must.