Do you accept this statement?
Suffice it to say that when abortion was performed at those times they probably did not think they were killing a human life.
If you accept that as historically true, then what would the founding fathers have done if they were to discuss abortion, having the medical evidence we have today and knowing that life basically begins at conception? Would they outlaw abortion completely? Would they outlaw abortion for all instances that were not rape/incest/life threatening to mother?
I think they would have tabled the discussion and compromised if it bogged down, like they did with slavery. They chose not to extend the protection of guvmint and extend the right to liberty to slaves because of political expedience. And for that, we ended up later with the civil war, ~400k dead or so. The abortion issue has given us ~100 times more dead, 2 orders of magnitude more. So if our founding fathers had been given that glimpse of consequences, I wonder if they would have chosen to outlaw slavery and abortion right at the outset. Of course, hindsight is 20/20.