The organism inside a fertilized chicken egg is a chicken. In an early stage of development, but it is no other organism. This idea that it is "some other" thing because they name the stage differently defies science. Now, that requirement may be changed in the future, but the chicken, at this stage, also needs constant support, that it gets it from the egg and from incubation doesn't change that it needs more than to "just be".Wait a minute here. To return to one of my favorite analogies, an acorn "has all it needs" to develop into an oak tree, but it is clearly not an oak tree. A chicken's egg is not a chicken, yet it is a self-contained system for producing a chicken. You have not demonstrated how the conclusion follows from the premise.
Unlike a chicken's egg, a human zygote cannot develop into a complete human being independently. It requires constant life support from a female human donor to develop. It is genetically complete but that's just one arbitrary point in the development of a new person.
Any more than the infant would need constant support.
That it must be incubated doesn't change what it is. It only changes the idea of "rights". Since at this time we cannot ex-utero incubate a human, the rights of the woman who must incubate them must be considered.