I can't say whether or not delayed O has caused an early miscarriage for me for sure, but since I started temping (before conceiving Marieke) I know that I always had a 12 day LP, and as soon as I went longer, I was pg. So since starting temping, (about 2 1/2 -3 yrs ago now) I've never had an early m/c due to delayed O. I generally have about a 35 day cycle, so I O on about day 23 or so. It seems that has made me somewhat less fertile (it took us over a year to conceive all three pregnancies) but we do become pregnant, and have not lost one yet. I have read that a late O can cause a "poor quality" egg, with a worse chance of a successful fertilization, implantation, and pregnancy, but I don't know what the actual research and statistics are saying.
Anyways, hope my little ramble helps, and hope you get a BFP soon. All the best!