My partner stayed home to look after ds, he wasn't working and I would earn more than him if I did so it seemed crazy not to do it this way.

One thing that used to drive me crazy - and still does - is that whilst he may do the childcare, he seems blind to the housework and cooking duties. I think if I have to earn the money, he should do the other half. I get really annoyed to finish up (I work from home now) to find the place a mess and no plans for dinner. If I want a decent meal for the family I have to cook it myself GGrrrrrrr.
Maybe set gudielines for sharing of duties if and when you do go back to work.
BTW you may decide you don't want to go back - office politics and the like get very tiresome after you have a baby! Also, you don't know what "kind" of baby you may get. I was another happy to "escape" a very colicky baby after 6 months, but now with a more settled baby I am getting a little resentful that dp gets to stay home and play.
Keep in mind I have a rather crappy relationship with dp anyway.

there are so many variables it can be quite hard to plan these things!!!