baby mama vs woman

baby mama and woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
baby mama	Yes	No	No	No
woman	Yes	No	No	No

As nouns, woman is a hypernym of baby mama; that is, woman is a word with a broader meaning than baby mama:

Other hypernyms of baby mama include female parent, mother, adult female.

baby mama (noun)	woman (noun)
the mother of at least one of your children	women as a class
	an adult female person (as opposed to a man)
	a female person who plays a significant role (wife or mistress or girlfriend) in the life of a particular man