obstetrician vs adult male

obstetrician and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
obstetrician	Yes	No	No	No
adult male	Yes	No	No	No

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

Other hypernyms of obstetrician include man, medical specialist, specialist.

obstetrician (noun)	adult male (noun)
a physician specializing in obstetrics	an adult person who is male (as opposed to a woman)