The argument the Supreme court made in Roe is that the right to privacy of medical decisions is protected, AND the unborn's right to life is protected at some point... so a balance must be struck to determine at what point the unborn's rights begin to outweigh the woman's right to medical decisions, they chose viability.
Right, I get that. And I also get there are two separate issues here. Does a woman have the right to an abortion, and at what point is that right NOT absolute. If the right is never absolute, then effectively the answer to the second is 'no' and Roe v Wade is gone.