If abortion is murder, then God spelled out his own ridiculously elaborate plan to Moses.
Numbers 5:11-31 in summary:
If a man suspects his wife of cheating, then he must bring his wife to the priest, and give him some barley meal, make sure it doesn't have oil or frankincense.
The priest takes holy water and mixes dust from the floor into it. The priest then uncovers her head, loosens her hair, and makes her hold the grain, while he holds the water.
He then says that if she's innocent, the water won't hurt her. But if she's guilty, it will bring a curse to her. It'll cause painful suffering, make her thighs rot, and her belly swell. She will become barren and miscarry any pregnancy she may have. And finally, the people will denounce her.
She is then commanded by God to consent to this. (Oh, well at least it's pro-choice! /sarcasm)
The priest writes the curses on a scroll, then washes the ink into the water. He makes the woman drink the water. He then takes the grain and burns it on the altar. Then he makes the woman drink again.
If she's guilty, the curse will take effect. If not, she'll be free and able to have children.
How's that for a plethora of thresholds? Or was that innocent "baby" not murdered?