Newborns are very sensitive to cold, but as long as they are being kept warm (central heating on, maybe a couple degrees higher than you'd normally set it) you should be fine. Just make sure that wherever they are, the heat is getting in the room. My mom unfortunately lost a litter of kittens this way when she didn't know about this, she had them in the basement because that's where kitty gave birth, and when the mama started bringing them all the way up the stairs and trying to put them in her bed, she thought she was just being cute/silly. Sadly, she was doing that because mama knew her kitty's weren't warm enough. She didn't want them to get hurt, and not knowing any better, brought them back into the basement. They passed. Not to scare you though, this can easily be avoided. The problem with my mom's scenario was that the central heating wasn't warm enough all the way down in the basement. And if you notice mama kitty trying to move the kittens to a different (warmer) area of the house, or tries putting them under her blanket or something, keep that in the back of your mind that could be why. But as long as it's warm, don't worry too much about it- a heating pad isn't necessary. If you have any questions, I've gone through this twice with a young kitty mama (1 year for first litter, second came a couple months later before we were able to get her fixed). Both litters turned out great, although mama had issues with not being attached to her first litter, so we had to step in. If your kitty isn't having that issue, I'd advise being a little hands off for the first few days- unless you have reason not to be. Just keep an eye on things, but it's best not to pick the kitty's up, or even touch them really in the beginning if you don't have to. It's a scent thing, and it's important to keep only mama's scent on the babies.
I bet she's a good momma.
