When do you change the litter after babies have been born?

Cats should not be using litter for at least 3 weeks after giving birth. Kittens should not be using litter until they are at least 4 weeks old. This is because the kittens' immune systems are not fully developed and they are more susceptible to infection. During this time, you can use a disposable whelping pad or puppy pads to absorb urine.