Very valid thoughts. This class is designed for a more advanced pre-natal client and one without health limitations and concerns during her pregnancy.
In regards to the bridging and supine work. If the woman is comfortable and confident, then yes, she can work in and through these ranges of motion for a short and limited period. Regarding the 4 point position, I personally have not had any experience or in my research any major concern about this position and a possible embolism.
As we know, movement, which increases blood flow and circulation is helpful in preventing a pulmonary embolism. If there is a concern during pregnancy, the program should be designed so that (as you stated) the positions are not being held for an extreme about of time and/or that the positions are not static, they include various additional movements - does that make sense?
The 4 point position is a staple of pre-natal work simply because it's comfortable for women and it allows them to do many exercises (back extension, spinal articulation and abdominal) in a position that is not contraindicated.
Please let me know if you have any additional questions.
Your question is common one, and there can be a lot of confusion surrounding diastasis recti.
First, yes, women with a diastasis recti can absolutely do Pilates. Many of the abdominal exercises will need to be modified to 1. heal the diastasis and close the separation as much as possible 2. to help them regain strength, control and movement integrity, which is mostly like compromised by the diastasis.
In saying that, sometimes a woman's diastasis or separation may never fully close, but with patience, time and proper exercise progression, she can regain immense abdominal/core integrity so that she can safely resume some flexion exercises. Does that make sense?
This is a very short answer for a very long one But I hope that it sheds a little light on the topic for you
Let me know if you have any other questions or need anymore details