OK, depending on the size of your dog, and the size and status of his unit, it may be more or less than 3 inches to the belly button.
And, even though Rob, and my girlfriend try to tell me about the host gestation, I won't hear it. Us non-scientists actually envision the whole process taking place in a petrie dish and an incubator. Put in the test tube, take out a whole living dog. Kind of like microwave popcorn.