The rabbis distinguish four stages in the fetus’ development towards personhood. For the duration of the pregnancy, until the commencement of active labor, “a fetus is like its mother’s thigh” (עוּבָּר יֶרֶךְ אִמוֹ).
The author of the Covenant Collection in Exodus knew the Laws of Hammurabi and revised them to fit with Israelite legal and ethical conceptions. This is clear when we compare their laws of assault in each.
David P. Wright