pang vs labor pains

pang and labor pains both are nouns.

Word	Noun	Adjective	Verb	Adverb
pang	Yes	No	No	No
labor pains	Yes	No	No	No

As nouns, labor pains is a hyponym of pang; that is, labor pains is a word with a more specific, narrower meaning than pang:

pang: a sharp spasm of pain
labor pains: a regularly recurrent spasm of pain that is characteristic of childbirth

Other hyponyms of pang include birth pangs, labour pains, afterpains.

pang (noun)	labor pains (noun)
a sudden sharp feeling	a regularly recurrent spasm of pain that is characteristic of childbirth
a sharp spasm of pain
a mental pain or distress