normal temp for a 12 day old?? (under the arm)

here you go.

Under the armpit you add a degree and in a baby this young if it gets to a 100.4 then it's considered a medical emergency and that lasts up until they are about 3 months old.

Newborns usually have their temp taken rectally, it's the most accurate way for them. But yes, normal is anywhere from 97.5 to 100.