childbed vs giving birth

childbed and giving birth both are nouns.

Word	Noun	Adjective	Verb	Adverb
childbed	Yes	No	No	No
giving birth	Yes	No	No	No

As nouns, giving birth is a hypernym of childbed; that is, giving birth is a word with a broader meaning than childbed:

childbed: concluding state of pregnancy; from the onset of contractions to the birth of a child
giving birth: the process of giving birth

Other hypernyms of childbed include birth, birthing, parturition.

childbed (noun)	giving birth (noun)
concluding state of pregnancy; from the onset of contractions to the birth of a child	the process of giving birth