I'm wondering if anyone can help me....Im very concerned and worried....

I went to my doctor today and was told that a certain blood test that I was suppose to take at 16 weeks and forgot ( I was moving and lost the form for the blood work) ....it has something to do with testing that baby for Down Syndrome....anyways...my doctor told me today that i am at high risk and that i am at 1/140....Im not sure exactly how high that is...or how worried i should be....I was offered to do an Amnio (sp?), but not quit sure exactly what that is or what if there is any risks of actually doing that....my doctor never said yes or no if he thinks i should have that done..he gave me the option....and im not sure what to do....Can ANYONE help me??....are these odd's of 1/140 high enough for concern or not?? any replies would be GREAT help....thanks!!

Alyson