Even premies who are born two months or more early are persons. Your argument is invalid.
Abortions after the limit of viability are very rare.
Only .08 percent of all abortions in this country take place after 24 weeks gestation ( which is the limit of viability).
They are the extreme cases. The cases where the woman's life is at risk or where irreparable damage to a major bodily function would take place if the pregnancy were allowed to continue, where the fetus died a natural death in the womb and it was not expelled ( yes, the removal of dead fetus and the fetal material is called an abortion and would counted in .08 percent if it was removed after the 24 week gestation mark) the cases where the fetus would be stillborn or is so malformed it will only live a few minutes or hours.
There were 323 legal abortions in Kansas in 2008 that took place after 22 weeks gestation.
191 of those of fetuses were not viaible. They had died in the womb, would be stillborn or were so deformed they would only live a few hours or minutes.
131 of those abortions were because irreparable damage to a major bodily function would take place if the pregnancy were allowed to continue. Those cases were extreme cases.