I don't think that you can cogently argue that the fetus maintain homeostasis and it certainly cannot reproduce.
As to the definition of life: You're right that it can be tricky. I think that the one that you gave applies just as well to a weed growing on your lawn and even amoebas.
As with all of us a fetus is a collection of cells. A fetus grows and develops by reproducing these cells. Homeostasis is a bit harder to explain. But, if you think of the fetus in terms of its parts rather than just the whole, I believe the definition of homeostasis applies.
Definition of HOMEOSTASIS
: a relatively stable state of equilibrium or a tendency toward such a state between the different but
interdependent elements or groups of elements of an organism, population, or group
As for the definition of life, the one I gave is not my invention. Here are the citations:
1.^ a b Koshland Jr, Daniel E. (March 22, 2002). "The Seven Pillars of Life". Science 295 (5563): 2215–2216. DOI:10.1126/science.1068489. PMID 11910092. Retrieved 2009-05-25.
2.^ The American Heritage Dictionary of the English Language, 4th edition, published by Houghton Mifflin Company, via Answers.com: "The property or quality that distinguishes living organisms from dead organisms and inanimate matter, manifested in functions such as metabolism, growth, reproduction, and response to stimuli or adaptation to the environment originating from within the organism."
"The characteristic state or condition of a living organism."
Are you suggesting that a fetus is of no more value than a weed in someone's lawn?