Such a tough one to answer as even if your doctor said ok, you NEVER know how YOUR pregnancy will go. I think that unless you had unusual problems, you could do the hard labor for the first 5 or 6 months. However, your abdominal muscles become stretched out and you cannot use them the same way you now do when you rake or muck out stalls. I bet if you paid attention to that work, you would notice how much your are contracting your abs to protect your lower back. After awhile you can't do it as well, no matter how hard you try. AND, toward the end of the pregnancy, hormones will cause your ligamented joints to loosen. This is to loosen the pelvis (at the pubic bone joint) to ease the passage of the baby.
There's no escaping the pregancy is really inconvenient. However, somebody's gotta do it, no?
AND, your ability to bring in an income will be impacted for not just the length of the pregnancy, but on and on, won't it? You will have to be able to make financial adjustments through the many years of raising a child.
That being said, I have two sons and cannot imagine life without them.
Horses are wonderful, but they are NOT children (I am going to get flack for that one, no doubt)
Where's your heart on this one, not your head?