For an interesting story regarding this..my own personal experience...
In 1993 I had a really nice anglo-arab mare that I had leased. She had done
quite well for me and since I liked her so much and she wasn't mine to keep.
I decided to breed her and continue to campaign her until early fall. She
top tenned the Land Between the Lakes 100 (her first) in early May and 3
weeks later was third (my choice) on a 75 miler getting also BC. 2 weeks
after that she did the Old Dominion in grand style, carrying me to a
wonderful, unforgetable 6th place finish (only the last 5 miles in the
dark!!!). I continued to campaign her on 50's and had her checked late
summer...bad news, said the vet, she's not pregnant. Oh well, at least I can
still ride her!!! Well, we went on to do several 50's, the Fort Valley 3-day
150 (second place behind Debi Gordon...in, I might add, the absolute WORST
weather conditions I had ever ridden in-sleet, freezing rain turning to snow
...mostly on top of very rocky mountains where you could only walk and were
too cold to even hold the reins). Then on to the SC 100 where we raced
(three of us) for 9,10 & 11th place (we lost by a nose) but finished in her
fastest time ever..about 9 1/2 hours!!!. She had off a few months and then
back into training...I even sent in an entry to the Tevis. April rolls in
and I used her to mark trail (50 miles) and had someone else ride her on my
2-day 100. Well, four days after that she bagged up and two weeks later
dropped a beautiful colt!!! Needless to say, I would have NOT ridden her in
competition after September had I known...the colt is now 2 1/2 years old
with 650 miles in utero!! Amazing what these animal can and will do inspite
of us!!!
Teddy
PS: The mare seemed to suffer no ill effects..the colt was weaned the day of
the Tevis(yes I withdrew) and I rode her to several other good finishes
before her owner took her back in the fall of 1994.