Bad mouth odour has nothing to do with you being pregnant.
It can be from very strong smelling foods, like garlic or onion or spicy foods.
From upset stomach, from a throat infection and also from problems with teeth and gums. If you suffer from catarrh that can also give you a bad odour in the mouth.
It is important to have your teeth checked out whilst you are pregnant anyway.
Wash your teeth in the morning and before going to bed and floss in between.
Seeing a dentist to have an orodental exam is advised.