"Viability" is such a horrible term too... As I shared on another related thread, since abortion is legal until the attending physician's estimation of "viability," if that physician is an abortion doctor, of course he'll decide a baby's not yet "viable." But if the doctors you're dealing with are trying to save a baby of the same gestational-age, like in the case of accidental early labor, obviously he or she is viable, and they'll do everything they can to save him or her.
And, ask a parent of a three-year-old whether their kid is "viable outside the womb", and the answer's 'no'. Because children require assistance to keep them alive.
Whether that assistance is just feeding, changing and bathing, or whether that assistance includes a ventilator, NO child under a certain age is "viable outside the womb". So it seems to me the only difference between "viable" and "not viable outside the womb" is whether a baby is wanted or not, and the justification and rule for determining abortion's legality is flawed from the beginning.