C.,
I would decide what you're really afraid of and go with your heart.
If the needle is what is frightening you and otherwise you would not have reservations abouth having the amnio then go for it.
I had amnio when 4 months pregnant with my daughter. Original testing came back with some scary possibilities and my dr recommended the amnio. I don't agree with the posters that limit the reasons for having/not having the amnio. Many are saying that if you have no intention of terminating depending on the results then "don't have it".
I didn't have it to determine whether I would terminate. I had it to prepare myself and the doctors for possible needs upon her birth.
The amnio did indicate some problems and knowing about them helped my dr care for her and myself. Knowing her situation my dr could warn me about symptoms that most women would think were normal but that I had to be very concerned about and get treatment when they occurred. I was able to take more precautions during my pregnancy that I believe saved my daughter's life.
The slight discomfort (some cramping)of the procedure was hugely outweighted by the comfort of knowing I was doing everything I could to produce the best possible outcome for my child.
I have never regretted the decision. I believe that there are no wrong decisions as long as you have all the info and follow your heart.
By the way, no early labor here. She came weeks late and finally had to be taken cesarean...a healthy 8 pounder.
Best of luck and take (of both of you)