Moving later into pregnancy, most women trade some of the exhaustion and nausea for new discomforts (yay!). This is when there are more positions and movements to avoid or become a little extra mindful about. The wonderful thing about Pilates is there are so many ways to make a single exercise safer, more effective, or simply more comfortable.
In general, most everything to be avoided isn't very comfortable at this point anyway; things like lying supine (on your back), strong adduction work (squeezing the legs towards each other), or working with the hips in a large range of motion. The pelvis begins to become more an more unstable as it opens up room for baby to descend and supports more weight. So the intensity of work it's able to support decreases. In general, it's a good idea to decrease resistance and increase assistance slightly for work throughout the entire body as all of the joints become looser and more unstable.
Twisting and abdominal work are both great throughout pregnancy when done mindfully. Naturally, range of motion with decrease as that tummy grows so it's a nice natural reminder not to go to deep or too crazy. Because everything throughout the core is stretching to the max as well as taking on extra weight, mindfulness is key. Likewise, stretching is so important to keep mama feeling good and to maintain some balance in the body, but it's easy to overdo it. So the breath and listening to the body come first.
Despite it seeming like there are so many things to avoid, there is still so much a very pregnant body can do (so long as there aren't other complications or limitations set by a doctor). Pregnancy can be a beautiful time to nurture and to challenge. And you can feel great, alleviating many of the common aches and discomforts that come along with growing that baby!