fetometry vs mensuration

fetometry and mensuration both are nouns.

Word	Noun	Adjective	Verb	Adverb
fetometry	Yes	No	No	No
mensuration	Yes	No	No	No

As nouns, mensuration is a hypernym of fetometry; that is, mensuration is a word with a broader meaning than fetometry:

fetometry: measurement of a fetus (especially the diameter of the head)
mensuration: the act or process of assigning numbers to phenomena according to a rule

Other hypernyms of fetometry include measure, measurement, measuring.

fetometry (noun)	mensuration (noun)
measurement of a fetus (especially the diameter of the head)	the act or process of assigning numbers to phenomena according to a rule