Question about gestation and foaling

[Magic Marker Miniatures]

My last mare is 12 days away from 300 days (based on first day covered). In the last three days she is bagging up quite quickly. She is a 28" refined mare so bag does not get huge.
How many days before 300 days can the foal be able to live without medical intervention. I know some breeders jave had mares foal before 300 and foal was healthy.
She has had one previous foal and she foaled on 320 days.
Here is her bag production in the last three days. First is Thurs, than Fri, and last is today. She is penned with our five other mares that have foaled and is fed alfalfa am and pm. The remaining time she is grazing on a pasture with no fescue.

 

[Becmar]

Get your self a ph test kit from pool store. Squeeze just a little milk and test it. When it drops below 6.5 (I think it is) she will drop within 24 hours.

 

[Magic Marker Miniatures]

I know that. She doesn't have any liquid out.
I was, at first, worried she was going to foal before 300 days.
Now I think she will be foaling between 300-330 days, allowing the foal to be full term.

 

[Ryan Johnson]

I was always told 310 to be safe . The longer over 310 the better .

 

[Magic Marker Miniatures]

She had her first and only foal at 320 two years ago.
She is moving forward a little at a time. She will be 300 on the 11th and will start staying in a stall at night.