I have read that early miscarriages are most likely to occur around the time your perios is due, so that would normally be weeks 4, 8 and 12 on a 28 day cycle.
I have quite long cycles (somewhat irregular) between 30-40 days. I have just had a late miscarriage at 16 weeks (problems started around 14 weeks. So, is it possible that because my cycles are long that this was the same as a 12 week m/c?
I had a scan at 12 and 15 weeks and all was fine, baby right size, placenta in right place etc. I am therefors guessing that the role of progesterone etc is done by this time and therefore the long cycle has no bearing, but I just wondered if anyone knew otherwise?
I also have irregular periods which are also over 30 - 40 days apart. The docs found it hard to date my pregnanvy because of this, and when i started to bleed, they said i was miscarrying, but could only tell me that i was anywhere from 6 weeks to 11 weeks preg. So IMO it is possible that you were earlier than what you thought. It is hard for docs to date a pregnancy if we have irregular periods.
Hope this helps a little, and hope you get the answers you need.