Definitely relax, and don't bother cleaning like she is going to want to look in all of your closets, etc. I was very disappointed my SW did not want to see the closets after I had them all perfect.
Be yourself, have the house cleaned like company is coming over (mostly the common areas and maybe the baby's bedroom, although ours was under construction at the time), and have a fire extinguisher and a plan in the home. It was not bad at all!
Good luck!