I'm in a similar (ish) position.
After a couple of early mc, around 6 weeks, I had one last January at 11 weeks (think the baby died around 9). The 'products' weren't tested, as the hospital was incompetent.
Then last September I had a missed m/c at 13 weeks, discsovered at the nuchal fold scan. I'd had a scan at 10 weeks showing a healthy heartbeat and right size. The PoC was tested, and showed Edwards Syndrome (a chromosonal thing, like Downs).
Before I got that result, though, I went to a private guy on Harley Street for tests, who diagnosed over-active NK cells, and prescribed steroids for 'next time'. Hurrah, I thought. It will all be OK.
Got pregnant in January, and had a missed mc last week at 11 weeks, having, once again, seen a heartbeat at 8.5 weeks. The baby died at 9 weeks. Harley Street man is mystified, but no doubt one of those harder-nosed Gill Lockwood types would say it's another genetic problem, what with me being old (41). I have yet to have results of this one back from the lab.
I don't know where to go from here. If it's another chromosonal prob, maybe I'll have to do the IVF where they select Ok embryos.