I did exactly this - took off a year off between 2nd and 3rd year - best decision ever. I guess I would try to review a little a month or two before you return. I had forgotten so much and didn't have time to review - really struggled in Medicine for the first month (psych and family went fine). I also recommend starting the year off with easier rotations so that the transition isn't so terrible for you or baby. If you started on psych - you'd actually have plenty of time to review then (and spend time with baby!). (Maybe you're super smart and remember everything and don't need to review - even better)
Make sure you have childcare set up with backups as necessary - hopefully you have family support. Babysitters and daycare issues tend to blow up at exactly the worst times... (right before exams, when you're supposed to be on call, insert worst case scenario here).
Congrats and welcome back. You'll get back into the swing of things faster than you think
I am def more relaxed about grades now too.