Of course it had to be all pink since she is having a baby girl. The only diapers I could find had blue edges, though, so I had to kind of overcompensate with the pink. :)
The bottom tier is made with size 2 diapers and the top two are size 1. (I don't like the idea of making the cake with newborn sized diapers since some babies are born too big for those.) Each diaper is rolled and secured, and then they're bundled together to make tiers. In this case, the bottom two tiers are bundled around a bottle. Then the layers are stuffed with goodies for the baby.