Hey that's awesome! I breed quarter horses, I love apps though and my father is anyone's best friend who is an appaloosa fan.
I've always been able to compete and ride with my broodmares, I just made extra sure they were sound, healthy and getting all the nutrients they needed, and that I didn't overdoe it.
I don't know if you know or not but try and give her "Rhino" shots the 5th, 7th and 9th month of pregnancy. It helps keep the foal from getting aborted.
And I personally would NOT give a broodmare ANY West Nile shots whatsoever. WN shots (among many others, including child immunization shots) have some terribly discusting, immune degrading contents. Check out this site if you're really curious:
Home
I've not only reasearched it online, but have seen it to. I've had several friends who had mare cycle problems also, when vaccinating with west nile. We previously had one gorgeous Anglo Arab mare that flat out stopped coming into cycle.
And for the most part -Good luck with breeding and raising! It's tons of fun!