Being present when a mare foals is a wonderful experience!
However, mares can be sneaky. :-) Their instinct is to have their foals in the middle of the night. Most mares foal between 11 pm and 6 am. Many mares have a way of foaling at 3 am when you think it is safe to sleep for another 2 hours, or you go into the house to make a pot of coffee. The best way to be present when the mare foals is to setup a cot next to her stall or paddock. If you are a light sleeper then you can keep an ear out for "unusual sounds". You might wake up many times a night (and not get a lot of sleep) but when she goes into labor - especially when she breaks water, you will instantly know that this sound is different and will be there, ready to assist if needed.
There are a lot of signs that a mare is close to going into labor or is in labor. Not all mares show all the signs. Sometimes a mare shows no signs and just surprises everyone with a foal in the morning!
The most common signs indicating that the mare is nearing foaling are:
Her udder starts to fill (and swell) 2-6 weeks prior to foaling.
The muscles of the croup, tail head, buttocks, and lips of the vulva start to relax 7-19 days prior to foaling.
Her udder's nipples start to fill 4-14 days prior to foaling.
The teats start to develop "wax" 2-4 days before. Waxing (or wax beads) refers to the sticky and drying drops of colostrum (first milk) which appears at the end of the teats.
Some mares will start dripping milk or colostrum 24-48 hours before foaling. Excessive loss of colostrum may result in an inadequate supply for the newborn foal.
Here is a site with more details about how to tell when a mare is about to foal. I have used the water hardness test strips with excellent results. (Be sure to use DISTILLED water - both to dilute the milk AND to rinse all your testing equipment before use so that you have no water minerals to throw off the test results.)http://www.omafra.gov.on.ca/english/livestock/horses/facts/info_foaling.htm
The above site refers to Stage 1 labor. I have found that most mares don't show obvious Stage 1 labor. I have watched over 20 foals born, and only once did the mare show obvious Stage 1 labor. Don't expect or rely on being able to tell if she is going to foal "soon" by watching for signs of Stage 1 labor. Odds are that you won't know she's actually in the process of foaling until she breaks water and starts Stage 2 labor.
Here are some important things to know about foaling:
1) Foaling happens REALLY FAST. You need to plan ahead for what you are going to do when you find your mare beginning to foal because you will have no time to contemplate what you are going to do next once she starts. (Once Stage 2 labor starts.)
2) If you don't have experience foaling consider moving the mare to a facility where someone with experience will be at hand when she foals. You won't have time to call someone to come help (see #1 above) - if she needs help things can go from bad to worse very fast, before anyone can arrive to help.
3) Even if you call the vet the moment you see her starting to foal, odds are good that when the vet arrives one of two things will have happened - either she foaled without assistance, or she will be in serious trouble.
4) You need a lot of room for the mare to safely lie down and foal and for you to have room to safely assist her if needed. A normal12x12 stall is WAY too small for a foaling stall. You either need a double stall (12x24), an extra large stall (e.g. 16x16) or a foal-safe paddock or small pasture with dry bedding (straw is best, don't use shavings or sawdust as they can cause breathing problems for the newborn foal) and fencing that the foal can't get caught in or roll under.
5) 90% of the time things go easily. But if your mare or your foal is one of those 10% cases, it can be a real tragedy. Please don't needlessly take chances and "hope" everything will be OK. Plan ahead. Prepare a safe stall or enclosure. Have necessary supplies at hand. Know the phone number of your vet AND your backup vet if your primary vet is involved in an emergency and can't come right away.
There are a lot of good books about foaling but I found the most useful "book" was the foaling chapter in How to be Your Own Veterinarian (Sometimes)
. Other popular books about foaling are full of advice like "call the vet". Yes, you SHOULD call the vet, but what should you do (or not do) while you wait for the vet to arrive? HtbYOV(S) tells you what you should or shouldn't do in situations like that.
Good luck with your mare! Please let me know when she foals. I LOVE foal photos. :-)