This is not about whether or not a fetus is alive. Every cell of your body is alive. You don't freak out when you clip your fingernails. Because your fingernails, although alive and part of a person, on NOT an actual person.

The same is certainly true of a newly created zygote. Whether or not or when that zygote becomes a person is a legitimate area of conflict.

The Constitution, of course, says nothing about the unborn. BUT it DOES refer to "persons born" in the 14th amendment when it talks about who is a citizen. To be a United States citizen, you must be born. At least acccording to the 14th amendment.