w/a newborn and a toddler at home, it's a wonder we've been anywhere in the last month - as it is, we've been out to such exciting locales as the surgery, the park and to Sainsbury's.
i don't think there's any 'rule' about leaving the house first month after you have a baby, but personally i'm trying to limit the exposure of my newborn during cold/flu season until she gets a bit older - and can have Calpol, Nurofen, etc. there's also packing up the kids to go out. No more popping out to shops, cinema, etc. Gotta make sure you've got all the supplies for them, car seats, jackets, buggies and such.
most times we just don't bother and only one of us goes out.