How long have you been waiting?
Im pretty sure 9 months is about the norm, but you don't want to be working them very hard.
.....although there wassssssssssss this horse at the track. She apparently had gotten pregnant when she was turned out somewhere and no one knew (how you don't know when they get towards the end of the pregnancy is beyond me!) she ran a race one night, raced very very good (i think she was 2nd or 3rd) and they came in the next morning and she had foaled overnight!
Crazyness..... obviously you don't want to do this, but it was an interesting story