Death of Newborn Rat

Question
Recently, (sometime during the night between August 13th and 14th), my rat Tallulah gave birth to ten squeaking bundles of joy. I made sure she was taking good care of them all and I was proud to see that she definitely was. Last night, however, (August 15th), I noticed that one of the pinkies was rather thin and pale compared to its siblings and I could clearly see what looked to be her intenstines through the skin of her belly. They seemed to be rather large to me and were yellowish in color but this little girl was thrashing around as much as the other babies so I just put her in with Tallie alone for a little while so she could get a chance to feed and crossed my fingers that she would be fine. However, when I returned home from work this afternoon I was saddened to find that she hadn't survived. Could there possibly be some sort of genetic defect or disease that can be attributed to her death or was it just the fact that she was smaller and weaker than the rest of the rather robust litter?

Answer
Its impossible to know what happened, but its not at all unusual to see this from time to time. Rat breeders sometimes see this with every other litter born. Sometimes none of the babies survive, sometimes they all live and do well. It depends on alot of things.  However, losing one is not unheard of.  It seems that there is always a runt in every few litters.  

One of my rats came to me pregnant, had 15 babies, all nice and chubby, and I found one dead a week later for no real reason.