Based on my experience, I'd say you're mad. I started postgrad when I had a 11 month old. Did a semester, had to stop after that with severe morning sickness. Went back with a 6 week old and almost 2 year old and struggled just with 1 subject. Dropped out after that.

Having said that it depends on how much you are willing to sacrifice and how much support you have, and the nature of your other work.