[quote=Jorick]If you want to talk definitions, defining all fetuses in any stage of development as parasites is 100% accurate based on the strict definition of the term: "an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense." They live in another organism and derive nutrients at the woman's expense. This is no stretching of the term, it fits exactly. [/quote]

Where it fails is 'at the woman's expense,' in that it implies this is a pure negative for the mother (most mothers tend to disagree). I would argue it's a symbiotic relationship. This allows for some 'parasitic' traits, but as a more general (and significantly less loaded) term, also acknowledges the positive aspects of the relationship.

Neither is technically correct, because all forms of symbiont (including parasites) are required to be of another species from the host; biologically speaking this is natural reproductive process, which cannot be categorized in either sense we're talking about. But, hey, language is cooler than science, so eff it.