Some parents believe in (or have been recommended) a “one parent-one language” approach to help their children learn multiple languages. This means that each parent uses one language when speaking to their child (e.g. Dad only uses English and Mom only uses Mandarin). Even though this is one possible approach for raising a bilingual child, there is no evidence that this is the best way.
A factor to consider will be how fluent a parent is with the language. Children learn language through the models that they are exposed to. If a parent uses a language that they are not comfortable with, this may affect the quality of the language input (such as the choice of vocabulary or sentences structures used) and the conversation may not feel natural.
So, use the language(s) that you are most comfortable with. And consider creating opportunities for exposure to any language that you may not be very fluent in (e.g. involving a grandparent who is more fluent).