Is this your first? (I am assuming he is yours. Not a dig, just don't have the back story and/or even know how long she has been your GF.)
I have three kids. We didn't start having them till we hit our 30s. Some of my old classmates are grandparents and our kids haven't even hit high school yet. (11, 9, and 6)
Anyways, the first is always the biggest shock to the system. Have fun...they grow up FAST!