gravidness vs maternity

gravidness and maternity both are nouns.

Word	Noun	Adjective	Verb	Adverb
gravidness	Yes	No	No	No
maternity	Yes	No	No	No

As nouns, maternity is a hypernym of gravidness; that is, maternity is a word with a broader meaning than gravidness:

gravidness: technical terms for pregnancy
maternity: the state of being pregnant; the period from conception to birth when a woman carries a developing fetus in her uterus

Other hypernyms of gravidness include gestation, pregnancy.

gravidness (noun)	maternity (noun)
technical terms for pregnancy	the quality of having or showing the tenderness and warmth and affection of or befitting a mother
	the kinship relation between an offspring and the mother
	the state of being pregnant; the period from conception to birth when a woman carries a developing fetus in her uterus