Hi OP, with DS2 we had a 1:288 'risk' and opted not to have the amnio as we didn't want to risk miscarriage. I spoke to my GP about the risk rate depending on who performs the procedure and he said the risk is what it is - the chances of infection etc don't lessen just because it's never happened to the doctor in the past.
It's a decision that only you can make. However, in what other situation would a .4% chance be considered high risk? It's very low risk IMO. This result would not be considered high risk in other countries, eg UK.
DS2 was born chromosomally normal.