Not going back to work

I had my baby on August 11th and was supposed to go back to work on the 16th of October. I have decided not to go back. I'm unsure how I'm supposed to tell my supervisor. I'm currently on unpaid leave so I won't be owe the company for any compensation. Am I obligated to go back and put in my 2 weeks notice or could I just go and meet with my supervisor to let her know?

I don't want to burn any bridges because I may need to use them as a reference in the future. My current job is really stressful and the hours are unpredictable and it's impossible for me to do that kind of work, take care of a new baby, and take care of home.