Amniocentesis option...your opinions/experiences please?

Catie
Hi everyone,
So my husband and I are expecting our first child (a daughter) and I am currently 22 weeks pregnant. The results of our triple blood screen showed I had a very slightly elevated AFP level of 2.53 (2.5 and below is normal for Caucasian women in my age group). As a result, we had a detailed ultrasound to look for spinal abnormalities. The ultrasound showed none. My doctor has cautiously offered us the option of an amniocentesis in order to be 100% sure one way or the other about the presence of spinal abnormalities. I am leaning against not taking this option for a few reasons. First, I am RH negative and the baby is likely RH positive. We are Americans who live in China where Rhogam is not available so I have already bought the 2 shots I need while in the US. This procedure would mean I somehow need to procure another shot. Second, my husband and I agree we would not terminate the pregnancy even if there was an abnormality. Third, I don't see the screening result as signifcantly high and have read that the triple test has a pretty high false positive rate. What would you suggest in this situation? Do any of you have experience with amniocentesis or an elevated AFP level? Feedback is really appreciated!
-Catie