Being a stay-at-home mom means you have one of the most demanding jobs in the workforce. You won't get a raise. There will be no clear performance reviews. And at least at first, you'll have to deal with a lot of bodily fluids (ideally, this aspect of being a stay-at-home mom diminishes over time).
Of course the major upside of being a stay-at-home mom is that you don't have to leave your children during the day and you have the joy of caring for and raising your children on a full-time basis. However, as gratifying as that can be, being a stay-at-home mom is not easy and you should think honestly about whether being a stay-at-home mom is what makes sense for you. Some of the challenges of being at home all day with young children are the exhaustion, the seemingly endless list of chores and always feeling like you look a bit of a wreck. Then there are the challenges of no longer working, like losing that feeling of accomplishment when a concrete project is finished, interacting with adults, and the obstacles you might face once you try to return to the outside workforce.
You'll never know if being a stay-at-home mom is really right for you before you actually try it. So do take advantage of your maternity leave, not just for your baby's sake, but to get a good handle on whether you want to stay at home permanently. Talk to other moms -- those who have chosen to return to an office and those who haven't; talk to your spouse and be realistic about the advantages and consequences of either choice. Whatever choice you do make, enjoy the time you do spend at home with your baby and make it count.