"Out of the woods" Age for Rat Pups?

Hello! We adopted two girls, who the owner was breeding, at the beginning of the month. We knew they were experienced Mama's, but we didn't exactly think one of them would be pregnant! But 24 days later and we were surprised with a litter of kittens. 5 in total, 1 stillborn. Mama never really liked us much so we're pretty nervous about stressing her out... But we're also anxious waiting to see if the other kittens pull through. No pictures yet because we're trying to give Mama and her litter as much peace and quiet as possible. At what age would you generally consider the babies to be "viable". As in, after this point they're probably gonna make it?

I consider all babies to be viable

The only thing would be if they have megacolon - a genetic condition. It happens in North America because of breeders, but I do not know if it is a problem outside of North America.
If babies have early onset megacolon you will start to notice symptoms once they start trying solid foods.
Babies with early onset megacolon need to be humanely put to sleep by a knowledgeable vet.
Rats with late onset megacolon can usually live good lives with a lot of support and a special diet

In my experience, it was after the first week. The first week was when the babies that weren’t going to make it didn’t.

Thanks for all the advice! I'm familiar with megacolon, so hopefully I can look out for the warning signs. I just didn't realize it's that common of a problem. We're currently watching for a litter from the female that was with Mama, and hoping this is it for surprise litters but who knows. I guess mama just had to give me a birthday present, and I was definitely surprised to find them! I share a birthday with the rats so I'm definitely partial to the babies already.

Mom is doing good though. She's nursing the litter, nervous with us around them but not aggressive towards us, and seems to be in great health.

Adorable! The same thing happened to me actually. I got a “male” buddy for my lone boy, and it just dawned on me all of a sudden that “he” was a she! I was so careful with the babies because another litter would have been a disaster, especially because she had 16 babies (10 that lived). I already loved her though so I just kept her and all the babies.

Those babies look good All dark eyed too it seems. What colour (coat and eye) is mom?

Being an experienced mom and not seeing any obvious runts or babies not doing well, I think you are in the clear now.

The mom is a dark eyed, hooded (heterozygous for dumbo we assume) double rex agouti. The father we know nothing about, but we'll assume for now the babies will look mostly like her. We did have a more experienced breeder in the area come to take a look, to ease our mind, and half of them are hooded and the other two look to be dumbo.