At the end of first tri (due to the ongoing risk of miscarriage - don't want to send them in panic mode until everyting is clear) and after the CVS results are back!
Depends on where you live: in Canada you can just opt to go straight to CVS and skip the FTS
All the FTS does is readjust your age-related risk. I want to know with 100% certainty: I'm a medical geneticist and do this for a living, so I've seen "lowered" FTS risks (1/500 for example) still being born with Down syndrome... Almost a curse to know too much