Baby talk among adults is a definite no-no in my book, but what about calling your significant other by a name no one else does? The nickname can be as simple as "sweetie" or as creative as "schmooky pie."
It can be conforming and natural to use a name that expresses affection for your significant other, as long as people around you don't find the constant assertion of endearment annoying. For example, some couples participate in an endless litany of "babes" — "Hey, babe." "Sure, babe." "Thanks, babe." — over, and over again.
How do you feel about using pet names?