Fionas, you could always take leave as planned and then spend more time on BellyBelly That is sitting down and more interesting than knitting. You could also read up on baby care while lying on the couch because it is not like you have much time to do that once bubs arrives.
My DS was born at 38 weeks. I am still missing those 2 extra weeks I thought I had to get the house ready. The house is still a mess!!!