All you need to do is nurse the baby back to health when a little skull comes up or treat the Adult if it is a big skull,
When you feed your adut it kind of spits food into the babys mouth to feed it
And you need to clean up their poops
and thats about it :kuribotchi:
But just a little tip that I have worked out:
If your tama has a baby and you leave it at school and the baby gets sick if you leave it for a while the Adult becomes weaker when it has a baby so it might die,