(19) I call heaven and earth to witness against you this day, that I have set before thee life and death, the blessing and the curse; therefore choose life, that thou mayest live, thou and thy seed;

Antoninus said to Rebbe At what point is the soul given to a human? Is it from the moment of decree [that such a child will exist], or from the moment of formation? He responded: "from the moment of formation." He replied, "is it possible that a piece of meat can last for three days without salt, and yet not become rotten? Rather it must be from the moment of decree." Rebbe said: "This thing that I learned from Antoninus, and there is a supporting verse: [Job 10] Your Providence has guarded my soul."

(22) And if men strive together, and hurt a woman with child, so that her fruit depart, and yet no harm follow, he shall be surely fined, according as the woman’s husband shall lay upon him; and he shall pay as the judges determine. (23) But if any harm follow, then thou shalt give life for life, (24) eye for eye, tooth for tooth, hand for hand, foot for foot, (25) burning for burning, wound for wound, stripe for stripe.

...the fetus is it's mother's thigh...

(7) If she miscarries on the fortieth day [since her prior immersion], she need not be concerned that it was a fetus. If [she miscarries] on the forty-first day, she should sit [for the required number of days] for a male and for a female, and for [being] a niddah. Rabbi Yishmael says: on the forty-first day she should sit for [the required number of days for one who gives birth to] a male and for [being] a niddah. On the eighty-first day she should sit for a male and for a female and for [being] a niddah, because [the formation of] a male is completed in forty-one [days], and a female in eighty-one. And the Sages say: this and that [are both completed] in forty-one.

If a priest's daughter was married to an Israelite who died, she may perform her ritual immersion and eat terumah the same evening! R. Hisda replied: ... She performs the immersion but may eat terumah only until the fortieth day. For if she is not found pregnant she never was pregnant; and if she is found pregnant, the semen, until the fortieth day, is only a mere fluid.

Mishnah: If a woman is about to be executed, one does not wait for her until she gives birth. But if she had already sat on the birthstool, one waits for her until she gives birth. If a woman has been put to death one may use her hair; if an animal has been put to death it is forbidden to make any use of it.

Gemara: But that is self-evident, for it is her body! It is necessary to teach it, for one might have assumed since Scripture says: According as the woman's husband shall lay upon him, that it (the unborn child) is the husband's property, of which he should not be deprived, therefore we are informed (that it is not so).

(6) Whoever sheds the blood of a human, By a human shall his blood be shed; For in God's image Did God make humanity.

(6) A woman who was having trouble giving birth, they cut up the fetus inside her and take it out limb by limb, because her life comes before its life. If most of it had come out already they do not touch it because we do not push off one life for another.

'If his head emerged' we do not touch him since we do not push away one life for another. Why? It is a pursuer (rodef)....A pursuer who was chasing another to kill him, say 'He is a Jew and a child of the covenant.' But the Torah said, 'The one who sheds blood, shall his own blood be shed.', meaning, save the blood of the pursued by the blood of the pursuer.

(9) ... It is a negative commandment that one should not protect the life of a rodef (pursuer). For this reason, the sages ruled that in the case of a pregnant woman in a dangerous labor, it is permissible to dismember the fetus in her womb - whether with a drug or by hand because it is like a rodef pursuing her to kill her. However, once his head has emerged one may not touch him, as we do not set aside one nefesh [soul] for another, and this is the natural way of the world.

There is nothing which is permitted to a Jew but prohibited to a non-Jew:...Concerning killing a fetus, a Gentile is liable but a Jew is exempt. But even though he is exempt, it is still not permitted. However, there is a difficulty for it says in Sanhedrin 72b, "if its head emerges, one may not touch it for the life of one may not be set aside for the life of another." But before its head emerges, the midwife may put her hand in the womb and cut it out limb by limb in order to save the mother. But this is not permitted to a Gentile, for they are liable for killing fetuses. And we can answer that it is a mitzvah for the Jew to save the mother and this might even be so for a Gentile.