When my mare Dream had Sassy, she bled out of her vulva for about a week. Sometimes it was just a trickle, then sometimes when she would lay down or roll it was like a huge flood. Our vet at the time said that it was normal. But, when I joked about it to a different vet, she thought it was rather strange.
Please notice this was 5 years ago, first foal we had, and whatever information we got was from our vet. So, don't jump my case if you find it necessary.