Di biologi, ada yg namanya intraspecific parasitism kok, gak musti beda spesies juga
Contohnya bbrp ikan deep-sea anglerfish, justru jantan itu parasit ke betinanya & jadinya disebut intraspecific obligate sexual parasitism
Yeah it might mimick a parasite, but calling a fetus parasitic sih, is quite misleading sih ya for me. And yeah Trophoblasts do invade and remodel maternal tissue, yes, but that's a specialized and regulated part of placenta formation, not simply an organism invading its host