Attitude and temperament are things to look for late in pregnancy. As there is less room in there for the foal to move around, poor mum starts to feel it a bit more. Probably best to hold off on the short rides for now. Her udder looks great and I've seen much smaller at this stage of a pregnancy , so she is doing great. You will notice it go up and down all the time. When shes up and moving around it will go down. After she has been resting or laying down you will notice it fuller. Once you are seeing it stay the same , you know you are getting serious.