Children add to happiness for many reasons, but one way is that they help supply a key element to a happy life: an atmosphere of growth.
  
Happiness Project

It's maybe too early to say, but it feels more like an adventure at the moment, than a fertile garden.  There are new discoveries (babies dream!  Their eyes twitch, and the breathing goes funny, just like Lottie).  There are challenges (how to change a nappy without hazardous waste spilling all over the place).  There is physical exertion (not eating, not sleeping).