my pet rat gave birth to only one baby?

Question
My pet rat had gone into labor, being a proud grandma I stayed to male
sure everything went smoothly. There was one problem, she only gave
birth to one. Not only am I wondering why this happened but she is
refusing to care for it. What can I do to save this little baby?

Answer
Refusing, flat out? Oh dear, not a good sign. Keep the baby warm (but not hot). I suggest a low-wattage heat bulb set a distance away from the cage and some fleece to keep the baby kinda cuddled in. Go get yourself some kitten milk replacer [KMR], and feed the baby every hour or so, as much as it will willingly eat.. but don't force it. After a meal, check it's belly to see the white milkband. If you don't see it, it isn't eating enough. Massage it's genitals gently with a wet q-tip until it eliminates (which may not be for a few feedings, but try after every feeding).

Unfortunately most babies that are orphaned are pretty near-impossible to save. It just seems to be the trend. But I really hope you have good luck with this one!