I had a mare who had given all of the signs of being ready to drop her foal. I fixed a light so that I could look out on her several times each night. As time grew closer, I put her in a cozy stall, with said light, shining into the lot so that I could check on her from the house. This went on seemingly forEVER. One night, things were out of sync, and I didn't put her in the stall, and forgot to plug the outdoor light in, nor was I able to check on her through the night; So she had no light shining on her (as was normally the case), no ME peering at her at all hours, and was free to roam her pasture as she pleased. The next morning I had a foal.