I think there is another basis to question the basis for the Row decision. Let me start with this quote from Blackmun's decision:
At this point the decision was reviewing historical precedent from ancient times to the present time of the decision. Contrary to some commentators, common law did address abortion, and it was not based on viability, but on a defintion of when life begins. As is clear in the quote, early common law set that point as the time of quickening, a reasonable standard that could be measured at the time with no instruments.
The protection of prenatal life shows up in this passage of the decision:
The court seems to recognize that there is a fight between the old common law beginning of life and the view that life begins at conception. In either case the court seems to acknowledge that the beginning of life is an important concern. Another key disctinction here is thant the recognition of interest in the start of life has now been replaced by the phrase potential life. The next key part follows later where the decsion construes "person".
At this point the historical documentation from prior to the 19th century seems to be disregarded. The common law meaning of persons from the beginning of life is now skipped, and with it any debate about where life begins. Shortly the decision returns to the beginning of life with this passage:
This is the first insatnce where viability is fully elevated as definition of life, and specifically given a date. Even though the court goes on to say that the law puts life at live birth, this nuance remains in its decision.
The court then sets two benchmarks, based on best medical knowledge.
I note that both of these points are due to medical science as it existed in 1973. This first benchmark is based on the relative mortality of abortion compared to childbirth, and this changes with advance in medical science. The second benchmark for viability also has changed substantially since 1973 as medical technology improves.
In my scientific view the decision is weak because it freezes facts that change with the advancement of medical technology. The court recognized that most viewed the debate about the beginning of life as falling between conception and quickening before the middle of the second trimester. Even so, the decsion took a specific dated scientific fact that placed viability outside this range, with knowledge that the science might change.
IMO, a stronger basis would be to invoke a definition of the beginning of life referencing best technology available, rather than a specific week from 1973 science. That would remain consistent with preexisting common law and provide for future improvements in technology to measure the onset of distinct human life.