Rtroops, I had 2 CHG embryos that both were early miscarriages, one at 6 weeks and one basically a chemical. I was told that although chromosomally normal,metabolically they may have been weak. I do think this is part of the problem as the embryo that eventually became my baby was a better embryo but I also added in clexane and aspirin to counter a clotting condition and I got BFP the next time.
I personally think one chemical with a CGH embryo warrants testing. They are so hard to get, so just cover your bases and do some basic immune and clotting tests.
Also check out your progesterone, as this is one of the main reasons an embryo won't keep going, I think that it is underrated a lot, but for some of us, our levels are not high enough so the pregnancy can't progress. Some clinics don't even test the levels and I think you should.