nativity vs live birth

nativity and live birth both are nouns.

Word	Noun	Adjective	Verb	Adverb
nativity	Yes	No	No	No
live birth	Yes	No	No	No

As nouns, live birth is a hyponym of nativity; that is, live birth is a word with a more specific, narrower meaning than nativity:

nativity: the event of being born
live birth: the birth of a living fetus (regardless of the length of gestation)

Other hyponyms of nativity include delivery, posthumous birth, posthumous birth, rebirth, reincarnation, renascence.

nativity (noun)	live birth (noun)
the event of being born	the birth of a living fetus (regardless of the length of gestation)