Once, again, you miss the point. A human being is an individual being. A fertilized cell may or may not be an individual being. It may or may not develop into a human being. We don't know. There is no available test to say a specific fertilized cell inside a woman will become anything.
You want to grant human rights to things we have no idea will ever become a human being and thereby diminish the rights of all human beings.
You are the one missing the point. Until/unless the zygote splits, it is a single human. IF it splits, then there are two (or more) humans. At no time is it NOT human. It STARTS OUT human: a living organism of the species homosapiens. Your concept of "may not become human" implies it is not human from the beginning. That is a lie.
And quit referring to them a "fertilized cell" you ignorant twit. The proper term, if you want to use the scientific label for their stage of development is fertilized ovum. Cells cannot become fertilized, only ova have that ability. Also, by thje 2nd day they are no longer a fertilized ovum, but rather a blastocyst. Like I said before, if you want to argue the science of it, at least learn the science of it. Right now you're spouting nonsense and lies and parading your ignorance around like it is some sort of award.
If you want to actually learn about the subject, a goos place to start is with this book:
Reproduction in mammals
edited by C. R. Austin and R. V. Short; ill. by John R. Fuller
Publisher: Cambridge [etc.] : Cambridge University Press, 1976.
This is another good one, but assumes an advanced knowledge of general biology and biochemistry:
Mammalian reproductive biology
F. H. Bronson
Publisher: Chicago : University of Chicago Press, 1989.
Of course, any reasonably comprehensive text on general biology found in most public libraries will have a section on mammalian reproduction, with enough detail to confirm that unborn are, indeed, human no matter how you personally feel about it.
Then again, if all you are interested in is continuing your lies and promoting killing innocent humans just because you can, don't read anything. Most proponents of abortion choose to live in ignorance.
But as an aside, lets look closely at your claims from a "what if you're right" POV. The only time a developing human can split into two identical twins is prior to the embryo stage of development. After that point, they have stabilized into the single human, set of twins, or triplets. IF your objection is "we don't know what they're going to become." then that lack of knowledge ENDS when they enter the embryo stage of development.
The embryo stage of development begins about the 2nd week of gestation.
So what excuse are you going to come up with for killing those unborn which ARE stable, unique individuals as of the 2nd week of gestation?