When should I take maternity leave?

So I'm currently 31.6 and I planned on working until I popped. But due to shitty managers and being all around uncomfortable, I wanna take it at 39 weeks unless he comes earlier. I told my bf and he tells me "whenever you're ready you let me know". My moms says 39 weeks sounds perfect if he doesn't come by then. Everyone agrees with me but my bf's mom. She thinks I should work until I have him just to have a little more money (not that we don't bc we have a lot saved up already). She thinks that since she did that with my bf that I can do that with our son, which I don't agree with. Does 39 weeks sound like an ideal time to take maternity leave?