maternity ward vs hospital ward

maternity ward and hospital ward both are nouns.

Word	Noun	Adjective	Verb	Adverb
maternity ward	Yes	No	No	No
hospital ward	Yes	No	No	No

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

maternity ward: a hospital ward that provides care for women during pregnancy and childbirth and for newborn infants
hospital ward: block forming a division of a hospital (or a suite of rooms) shared by patients who need a similar kind of care

Other hypernyms of maternity ward include ward.

maternity ward (noun)	hospital ward (noun)
a hospital ward that provides care for women during pregnancy and childbirth and for newborn infants	block forming a division of a hospital (or a suite of rooms) shared by patients who need a similar kind of care