in my first experience with a mother cat having kittens i learned that kittens die without the warmth of their mother, as their bodies do not have mechanisms to generate any heat (and cats in general have weak heaters inside them, they are nearly cold blooded)

and yes, usually cat mothers eat the cold dead babies that didn't make it, similar to the pig

and btw, 1/3 of kittens usually die, and they are eaten by the mother, most people don't even know this