-to-be
adjective
 (in combination) about to be; future
⇒ 
a mother-to-be
⇒ 
the bride-to-be
-to-be/-tə-ˈbi/ (say -tuh-'bee) 
adjective
future (especially in combination):  ◆ mother-to-be.
See: -to-be
-to-be
Suffix
- Future, later, expectant.