Well, keep in mind that unless she has the best support system in the world (that is not you), there will be a lot of sleepless nights, being “touched out” from holding a baby all day, a toddler to run after, lack of funds, sick child/missed work, a jealous kid that wants his mom all to himself, “You’re not my dad”, and possibly another kid who is biologically your own because once more she messed up the birth control.

I’m not even touching on the potential resentment from your end. Supporting an instant family, not being first, etc.

It’s easy to fall in love with the IDEA of having a family. Just as you fell in love with the IDEA of this woman. Just please only set up the crib and don’t sign any marriage certificates or open a joint bank account.