So I went through the same thing with my son at this age - anything about 99 freaked me out, but the doctor said that babies temperatures can fluctuate drastically because they are so small! 97.6 - 100.4 is completely normal... Another factor is whether or not you are taking her temp rectally. Rectally is the most acurate, but keep in mind that it may strike you as a drastic change because rectal readings are typically around one degree higher than any other method. Take regular rectal readings when you think she is running a fever to detect any change.
If she is acting fussy, won't smile or laugh for you, or isn't eating normally: call your doctor immediately. Otherwise if you have no reason to believe that she has been exposed to something or that she is acting sick in other ways, she could just be a little warm due to many factors.
Don't second guess your gut though: if you feel something is wrong, call your doctor!
at 3:14 AM on Jul. 8, 2009