It really comes down to personal choice and how you are feeling. I finished up work 3 weeks prior to having DD, had quite a demanding job and i was so tired, but I did have to keep jobs for myself to do to prepared for out new addition for me time off so as the time didn't drag more than it was already going to!!! I think 4 weeks is a good amount of time to finish anything you need to and most importantly rest as much as possible! It will also be good for you to take the extra time just incase your bundle decides they'd like to meet you a little early!

Hope all goes well. Enjoy the second half of your pg, its such a beautiful time in your life!