Madeleine,You are an extraordinary person with a strong work ethic. You are facing the same situation many heart patients are confronted with at some point in their lives. How to adjust work / life balance for your long-term health? I suggest you discuss your condition with the head of the obstetrics group to determine if there is another role or position you can preform and contribute to the team.
I don't have LVNC nor have I ever been expected to work 24 hour or night shifts, but I am a 73 year old man who has lived through a lot and learned some lessons along the way, and I hope you will forgive me offering you some fatherly advice about your "princess" midwife concerns. A very wise person once said that whatever anybody else thinks about you is none of your business. That is absolutely correct.
You need to do whatever is right for you and not make the mistake of concerning yourself about what others think. If others don't understand what and why you do something, that is their problem, not yours. You live your life, the best way you know how, without concerning yourself too much about what others who don't walk in your shoes may think.
All the best to you, including a long, healthy and fulfilling life. And welcome to Mended Hearts.