Blimey, some of these really are heart-rending.
We started ttc in my late 30s, found I had fibroids and got that sorted. Decided to go for IVF with PGS at 40 - no infertility diagnosis, but didn't want to do natural/transfer with high risk of chromosomal abnormalities.
It took 5 months and 3 rounds of stimson/collection to get enough embryos to test. Only one was normal. It was also a good, hatching blasto by the time it went in. We were pretty optimistic when we got the bfp- after all, in the absence of obvious health issues, genetic problems are the usual reason for mc, and we'd bypassed that.
Then my DP rang me at work to say he'd had a call from the cons' office - that the HCG wasn't rising and we should prepare for the worst. Cons didn't prepare me for the possibility of a MMC - said it would all end with a heavy bleed. Well, it didn't, and for 2 weeks I had a faint hope that the embryo had survived after all, before checking in with Dr Google. Just over 6 months from start of IVF to ERPC.
Our story did ultimately end happily, though. For various reasons, I lost confidence in my cons after the above, and we changed clinic. Halfway through another stretch of banking-for-PGS, someone mentioned immunes - and sure enough, I turned out to have thrombophilia and raised nk cells. 5 months of banked cycles at the new clinic resulted in bfn; but I persuaded my cons to prescribe me the thrombo/immunes drugs for a natural try pending getting back on the IVF horse. While obviously nervous at a bfp given 1) my history and 2) being 41, things were mostly uneventful after that, and DD is now sleeping next to me.