Which Babies are you asking about?
There have been three very different types of "Baby" Pokemon in the Pokemon TCG.
First, introduced in the Neo Genesis set, were actual Baby Pokemon.
If you look at the Pokemon stage, it says "Baby", not "Basic".
This type of Baby had an "evolves into" text box that said what Pokemon you could evolve the Baby into.
So this type could evolve.
Next, in the Ruby/Sapphire sets, they introduced a type of "Baby" that was a Basic evolution stage, but each one had a "Baby Evolution" Poke-Power that allowed the baby to evolve into the corresponding Basic.
So this type also could evolve.
What you are probably asking about are the current "baby" Pokemon introduced in the HGSS set.
There is no evolution info text box.
There is no Baby Evolution Poke-Power.
In short, if a card has no mechanism on it, or on the evolution that it is supposed to evolve into, then there is no way for it to evolve.
These new baby Pokemon are Peter Pans. They never grow up.
