Yoma 8:4

We don’t make children fast on Yom Kippur but we train them a year or two before they reach the age of majority in order to accustom them to the mitzvos.

Yoma 8:5

If a pregnant woman smelled food and developed a powerful craving, they feed her until she overcomes it. A sick person is fed according to doctors’ orders. If there is no medical expert around, they feed the patient as he desires, until he says it is sufficient.