Mares can hold onto their foals for around twenty five days after due date, till conditions suit them for foaling down. The weather, environmental stress, including human interference, can disturb some mares and make them very loath to get on with it.
Some mares wax up at their teats before foaling, some don't. There will be observable changes in the mare's mammaries but, again, there is much variation between individuals.
In short, there is no way of precisely predicting an imminent foaling, other than by tests to reveal hormone levels. Even then that is more likely to tell you when she isn't going to foal than when she is.
You may be surprised how many maiden mares just foal quietly, usually in the early morning without needing any human aid, although it is, understandably, a tense time for the owner.
Both of my foals were born outside, in April, and got to their feet and sucked without any trouble. The mare cleansed after each, no trouble, and, after a few hours of peace, was quite happy to allow us to handle her foals. I work on a stud, also, and we've had very few problems over the years.
There are many considerations when foaling mares, but the most important one, given that the foal is born and viable, is the cleansing or afterbirth. You only have about six hours before you have to react very quickly and definitely if your mare hasn't cleansed by herself by then. If you call the vet at that point, he still has time to get to you and deal with the situation and expect a positive outcome. Failure to assist her within ten hours is neglect.
Never attempt to pull a cleansing from a mare if she doesn't seem to be getting on with it. Rather, double it up upon itself and tie it up off the floor with a piece of string or baler twine. This allows the force of gravity to act on it and aid the process, whilst keeping it fairly clean and free of contamination from bedding/soil.
If the mare seems to cleanse herself, you must carefully lay the cleansing out on the ground and try to determine that it is all there, and that there is nothing retained by the mare. When laid fully out, you should easily identify the twin horns of the uterus, and the open ended uterus which housed the foetus. A cleansing looks a bit like an old-fashioned pair of ladies bloomers; a common description.
If at any point post-birth, your mare should show signs of dullness, raised temperature, or colic, you should suspect a retention of some of the cleansing, and urgently seek veterinary assistance. Failure to do so may result in serious consequences for your mare.
Once the foal is on its feet and sucking, you may wish to leave mare and foal together without disturbance so that they can bond. Some mares are very 'foal-proud' and may not want you anywhere near their foal, whilst some are quite at ease with visitors, but be careful as some newly-foaled mares can be dangerous.
Hopfully everything will go well for you all, and you will get a strong foal and a milky, loving dam, but if you do encounter problems, a good vet is your best friend.
