Systems Biologist here. Did my Ph.D. discovering how cellular signals arange in space and it's implications on cancer. I currently run a researxh group on liver toxicity and signaling.
The first issue with your argument is that life does not 'begin' anywhere. It is a continuum at the cellular level. Cells make copies of new cells. In many organisms , sometimes they change the number of chromosomes they have - going to one genome set (haploid) to having two genome sets (diploid) in metazoans.
In animals this trick is used to increase genetic diversity in an organism by combining the genome sets of two distinct individuals. This is sexual reproduction. I assure you, everything in this process - from the parent egg and sperm cells , their combination and the development to an embryo consists of cells that are alive.
So the where does life begin question is a little meaningless. The start point is arbitrarily defined for convenience/convention. A bit like how time zones begin at Greenwich Mean time.
That out of the way, it is important to note that an individuals body will terminate its own cells by a variety of mechanisms. Cell death is an important aspect in maintaining a healthy human body. Cell death is what sculpts your fingers, prevents you from succumbing to infections, prevents your immune system from destroying your own body...the list is endless. In that light, after fertilization, the embryo is as much part of a woman's body as her own hair follicles or skin cells. Even as a fetus, it remains completely dependent on the mother and is actually rather like a parasite. If she has a right to cut her hair and scrub her skin, terminating an embryo is not conceptually different. It is not even literally that different since abortion involves mainly scrubbing of uterine epithelium (called the endometrium).
Finally, abortion is objectively speaking an act of causing cell death by a neural/mental impulse for protection (economic / psychological /physical) of the parent organism.
Many pregnancies are terminated automatically through hormonal and cellular signaling pathways if the mother's body is not ready or capable for it. Abortion is simply a neural route of achieving the same result in response. A brain response is as much part of an individual's biology as their hormonal response.
Thus from a scientific point of view the entire pro-life stance is meaningless.
My purposefully strictly objective answer should at least convince you that this is not a scientific debate. It is an ethical debate. As such, it is subjective and you are not going to convince anyone who doesn't want to be convinced.
