Living cells do not per se have a right (protected freedom) to life for the same reason a virus or a mouse has no right to life.
Rights are a recognition of requirements for a person to live as a human which means freedom to think and act toward sustaining that life. Non-humans do not have rights, because they are incapable of recognizing rights. Without that recognition, there can be no rights, as their abrogation would immediately ensue through force, coercion, and other manners of violation.
A fetus is not yet capable of living in any way as a thinking, acting person in that sense. Therefore, it has no rights to do so.
As litmus test, can a fetus given rights (freedom without mom) perform the most basic biological acts of sustaining its own life? No. The fetus cannot oxygenate its blood, eliminate its toxins, convert food into a form that can power its cells, and any number of other biological functions that mom is performing on its behalf. If given the freedom to live as a person per se, the fetus cannot perform the most basic actions to sustain its life, it does not have rights, because no recognition of such requirements for it to live and no protection of its freedom will make any difference. The fetus does not need freedom at this stage in its life; it is entirely dependent on its mother.
To artificially bestow a “right” to life on the fetus is merely granting an entitlement to enslave the life of its mother, if the mother does not consent to participate in the pregnancy. This would not be protecting anyone’s freedom—only taking freedom away from the mother.
I am anti-abortion and pro-rights. Therefore, I am for a woman’s right to choose, no matter how much I dislike abortion. My opposition or dislike for something does not automatically mean support for government action to outlaw it. Because the law must exist to protect individual rights, any law that would abrogate rights must never be passed.
My position on abortion is consistent with other similar positions. I am an anti-smoking non-smoker, but I oppose legislation that would ban smoking. I am anti-drug and I do not use drugs, but I oppose the war on drugs. These positions consistently recognize that the law must exist to protect individual rights, not to trample on individual liberties.
When does a fetus become a person with rights? I believe the earliest that can happen is when a fetus becomes viable. That is, when it is medically possible for the fetus to survive when physically separated from its mother. This may involve the assistance of medical devices, medication, and extraordinary measures. The key criterion is the ability for the baby to live without being tied to the mother’s life. At that point, the baby’s life can be sustained by other means, and adoption becomes an option. As medical technology improves, this may happen at earlier stages of gestation. This would be the reasoning behind objecting to late term abortion.