One of the things I've noticed from years of online debate is that even the most staunch pro-lifer usually allows that a women abort in the case of rape, incest, or if the mother is in physical danger. The problem I take with that is that if their position is based on God's will and that God already knows that child, they are removing the idea that the women being raped and getting pregnant was part of God's will. They are removing the idea that the act of incest was God's will. They are removing the idea that God is choosing that baby over the life of the mother. In other words, they are deciding that a woman who gets pregnant because the condom broke would be horrible for wanting to abort because God loves that baby and it is God's will that she have it, but a woman who gets raped by her father and could die if she carries the baby to term is carrying a baby that God doesn't seem to care about and her baby is outside of God's will.
To me, you have to choose. If your reasons are based on God's will then you have to admit that in the case of rape, incest, or danger to the mother the baby is still loved by God and part of God's will and the mother shouldn't be permitted to abort. If you think abortion is okay in the case of rape, incest, or danger to the mother, you have to admit that God doesn't know and love unborn fetuses and that some pregnancies are outside of God's will, therefore creating a lovely shade of gray in which a woman has to be permitted to make her very own decisions based on her own life.
I think that people who have carried a baby to term and loved that baby want to believe that that baby was always a baby, that God always knew and loved him.. that there was never a time when he was less than the wonderful little thing that he now is and there was never a time when he was "soulless". However, if they were to miscarry a baby in the first half of pregnancy, while they would certainly mourn their loss, they are not likely to have a funeral for that baby. Why? Because deep down they know that at that point their "baby" was an idea of a baby and the possibility of a baby but was not actually a baby. Deep down they know that there was hope of a human life but not an actual human life yet. Even the mother doesn't mourn a miscarriage with the intensity that she would mourn the death of a her child.
I feel very confident that I have lost track of the point of the OP, and for that I apologize. While discussing God's will, though, I think it is reasonable to point out that through the entire Torah it is made pretty clear that someone who takes a human life should be put to death, but in the below verses you see that if someone causes a woman to miscarry but causes no other major injury to the woman, he must pay a monetary fine but is not put to death.
Exodus 21:22-23, JPS Edition
When men fight, and one of them pushes a pregnant woman and a miscarriage results, but no other amage ensues, the one responsible shall be fined according as the woman's hesband may exact from him, the payment to be based on reckoning. But if other damage ensues, the penalty shall be life for life...
In other words, he didn't have to pay a "life for a life" because the miscarriage didn't result in a loss of life. Clearly there is a big difference between a fetus and a human life according to the Torah.