Kudos on being such detail-oriented planners!

One additional thing you might want to consider is that your spending patterns while not at work may be different than your usual patterns.

Thus, if either or both of you stay at home instead of going to work during the relevant period, your commuting costs will decrease, as will such costs as lunches, coffees, etc. You will also likely be going out less during baby’s first few months that you normally would. On the other hand, you might pay more for pay-per-view movies at home, and on those occasions you do go out you may need to pay a babysitter, etc.

The final tally may be a wash, or it may result in either more or less spending. That totally depends on how you normally spend and how you would spend when you have your baby.