Hi FA, I had my bypass on Saturday just gone and guess what...24hrs before I got my period! Marvelous! I phoned to asked whether this would be an issue and the nurse said not at all, they just don't like tampons in the operating theatre so will give me a pad and knickers.
Strange thing was, 2hrs before surgery, the bleeding completely stopped! I had a pad and knickers in theatre but these had vanished by the time I was in recovery!!
No catheter or anything.
Anyway bleeding then returned 24hrs later for a couple of hours before disappearing again. Very weird.
I think Indianlight is right, your body just goes into shock and does it's own thing!
Good luck with everything,
Cuppa xx