I have the same issues. I am 6 months pregnant, but my horse is too unpredictable under saddle to ride, and I have chosen not to ride any horse at all during my pregnancy anyways.
What I do with my horse is light groundwork, in short spurts, more for his sake than mine (and he learns so dang fast I'm running out of ideas, lol).
Anyways, I lunge him, focusing more on his extension and muscle building than anything. We are working on getting the proper muscles to hold a canter at the moment. I work off of my voice as much as possible, and then the line, and then a whip, if needed. Stay consistent, doing lots of up and down transitioning and changing directions. I like my horse to slow down when I wiggle the line and say "easy" and to stop and face when I say "woah." I know these things will help under saddle.
Another thing we have worked on is yielding hind and front on the ground, and flexing. I start by asking my horse to stand next to me. I stand at his whither and then tug gently on the lead rope. He then stands in place and looks over at me, his head completely facing me. It may take some time if your horse does not already know how to do this, but its easy to teach. Simply apply pressure, and when they move their head, even slightly, release said pressure. Repeat, repeat, repeat, asking for a little further bending every time. Then switch to the other side.
After you have that accomplished, add the hind yield. To do this, ask for the flex in the neck, and then hold the flex and gently rub the side of the horse, about where your calf will hit her if you were in the saddle. She should move away from the pressure, and will cross her hind legs in the process. Release all pressure, including the head pressure. Once again, repeat on both sides.
These two exercises help to get a good one rein stop in as well, when you eventually start riding again.
When you have that accomplished, you can ask for a front yield. This one is a little harder for them, but it is very useful. Start by holding the lead rope loosely. Stand on the left side of your horse. Put your left hand on their neck, right where their head meets their neck on their throat, and the other hand on their front shoulder, right where you would put your foot if you were asking for a yeild in the saddle. Gently push with both hands until your mare bends her head away from you. Release pressure and repeat, asking her to go a little further with her head as she moves away from your pressure. Eventually, she will move her left foot over to compensate for her head throwing her off balance. This is what you want. Praise her, and keep repeating. She will get to the point eventually where she is crossing her front feet with a simple nudge on her shoulder,which can come in handy when you are riding her later on.
Other things I do to help them yield their front is what I like to call a half circle. Stand with your back facing a wall. Have the horse on a long lead rope. Ask them to start by heading to your right at a fast walk or trot. They will do so, if trained to respond to a whip or cues, and will eventually stop when they hit the wall. The moment they stop, they will still have energy from the trot. At this time, point the whip or crop, or carrot stick, towards their shoulder, and shake it while moving towards their shoulder, asking them to move away. If done correctly, with a horse whose front end is not bound up, they will cross their feet to get away from the pressure. Repeat going to the other side, having them start on your right and end up on your left. Ask for that yield immediately as the horse starts to stop. It takes a while for the horse to get what you want, but the results are awesome. If the horse ever gets stuck, then simply reverse them and try again.
Also I have done join ups, gone for walks, carrot stretches, and practiced squaring up and trotting in hand.
Sorry for the long post, but I feel your pain with the not being able to ride them, so I wanted to explain thoroughly how to do what I am talking about.
** Don't be the rider who gallops all night and never sees the horse that is beneath him **