To the best of my knowledge, there is only ONE scenario when PBA is the best solution. (I can't remember what it's called right now, but I *think* it's hydrocephalus.) The baby's head can be HUGE (think basketball) and impossible to deliver. The baby hasn't developed a brain and the head is over-filled with fluid. The PBA is safer for the mother than a C-section and preserves her fertility for a later try.
In these very RARE situations, when a baby has failed to develop a brain AND has hydrocephalus, I believe that PBA is the best way to resolve the situation. (Actually, I believe that this was what it was developed for in the first place.)
That said, as long as PBA is legal, it will NEVER be confined to these rare, horrible tragedies. It will be abused as such thing always are. Any PBA ban must include only this situation and then lock the door tight.
Have you had a child with Hydrocephally?
I have personally known 2 women who did. They both had their children. One had her son for 6 months. She keeps his photo on the wall. She and her husband loved him. They cared for him and were so happy to have had the chance to know him, even if it was a short time. My friend is now a counselor, who helps other people deal with grief. She knows what grief is. She knows what disappointment and loss of hope are. She has been through it, and come out the other side! She went on to have 6 other children!
My other friend had a doctor who told her that she needed to let the baby starve to death, so that she didn't prolong her "misery". She loved her baby. She didn't care what the child was like. She refused. She kept feeding and loving the child for weeks--under constant pressure from her doctor and family to let her baby die. Her husband gave her a very hard time about feeding the child. He hid the bottles and made it very hard for her. Unfortuately, the baby died after a few instances of her arguing with her husband. My friend has felt guilt for 15 years over this. It ruined her relationship with her husband and they divorced.
Death is a part of life. A part that we must face and not avoid. God gives us many lessons and blessings in the midst of that struggle, that we miss if we try to avoid it. To give birth to a child, and while it is still in the birth canal, to crush it's head and kill it, because it was deformed, will leave a person with guilt and sorrow for the rest of their lives.
Whether a person is "wanted" is not a reason to decide the value of their lives. Their lives have value because they are created by our Creator.