Tetanus can only occur in the absence of oxygen- thus, in this case there would have to be actual blood, not just a red area, which is quite normal, and that would would then have to close around the infection.
Unless there were clinical signs of tetanus a Vet would be no more able to foresee such a happening than would I.
By all means call the Vet if you are worried, I think any of us would do that, if I am right however what you are asking is, is this normal or do I need to be worried??
My answer remains the same- we all worry, whatever, the first time I saw this I had a small breakdown but managed to persuade myself to wait and see what happened, since, if she were aborting, there would be nothing I or anyone else could do.
My mare was fine and foaled three days later, without any problems.
If your mare were prolapsing she would need to abort to do it and, hard though it may seem, you would know by now, and NOTHING a Vet could do until it had happened.
Sometimes experience actually does count
