AmyNation
Road Warrior
Abortion laws are based are 2 concepts, viability, and personhood. If it can survive outside the womb, it can't be aborted. If it has a fully functioning brain, it can't be aborted.
Babies can and have survived at 21 weeks, and the babies brain is not considered fully functioning until 25 weeks.
The youngest baby to survive was 21 weeks and 6 days.
And determining the exact age of a baby in utero is not 100% accurate. When I was pregnant with my daughter I had 2 doctors and they had very huge differences how far along they thought I was, even while I was delivering I was either 8 days overdue or 2 days early, depending on the doctor you asked.
So, if a child can live at 21 week, making the cut off point 20 weeks seems like a nice safe zone.