EJE, I have had two IVF with PGD. I don't know why they'd say lower odds because the embryos are tested to see if they are normal. Perhaps they are talking about the drop in numbers goes quick because of the extra testing and time.
I found the numbers do go quick because of looking at fertilisation rate firstly, then how many can be biopsied at Day 2, then looking at how many embryos are normal, then it's finding a normal embryo that goes to blast. Numbers can drop fast.
So really, it has to be a tough embryo that makes it that far!

Saying that though, I have had 3 transfers (2fresh, 1 frozen) and haven't had success yet, but I have another 3 normal snow bubs yet.

On my last one the embryologist said they usually expect 20% normal. I actually had 50% so am happy with that result.

And it costs a lot too, mine is $2,100 with no Medicare coverage. Ouch!

I hope you get some good results on your PGD cycle. As I said, I'll be interested to see your numbers also.
Take care