midwife vs adult female

midwife and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
midwife	Yes	No	No	No
adult female	Yes	No	No	No

As nouns, adult female is a hypernym of midwife; that is, adult female is a word with a broader meaning than midwife:

Other hypernyms of midwife include nurse, woman.

midwife (noun)	adult female (noun)
a woman skilled in aiding the delivery of babies	an adult female person (as opposed to a man)