WTH,
I know we have had some PM discussions re PGD and I since looked back at Monash IVF info. They test for quite a few more than the "regular" trisomies, including 15. I know the chances of you getting 15 again are probably low and it could be any other trisomy but may help to ease you mind if you got the clinic to add a few more to the test group. They can test for every single chromosome - presumably you would just have to pay whatever extra.
PS. Have you found anyone else on BB who has actually done PGD? Would be interested to chat with a group contemplating PGD or have done