This refers to the time around 24-28 weeks when the child could survive outside of the womb. Most newborns don t apply for jobs, build themselves homes, and go down to the local grocery store to shop for snacks. Viability is defunct because must of us probably couldn t survive on our absolute own until we were ten or eleven. If we are going to define our rights as contingent as when we can survive on our own we should take rights away from all people who are in hospitals or in comas. Using their logic anyone who isn t completely self-sufficient must not have any rights.
Second viability is something that is only contingent upon modern technology.
Viability is contingent upon modern medicine and medical advances made on a daily basis. In two years from now we might be able to date viability at 15 weeks. Human life and personhood thus begin at conception. If we are only people when we have brain waves and heartbeats we must conclude that all of us must stop being people and begin being people again and again. Whenever we hiccup our heart momentarily stops.