This is a long shot but has anyone had a horse that has seizures and is pregnant?  If so, what meds did you use to treat the horse to have a safe birth.  

Had a horse with seizures yes, but he was a gelding. Loud noises, flashing lights ( Like turning on a barn light after it was dark) he would have a seizure. Throw himself  down. If he was inside stall he would hit the walls or hurt himself going down. We tried one medication and didn't stop them so we put him down before he broke a leg or worse. 

It may not be seizures, it may be that he's not getting the sleep he needs where he actually lays down.