Septuagint Exodus 21:22-23
And if two men strive and smite a woman with child, and her child be born imperfectly formed, he shall be forced to pay a penalty; as the woman’s husband may lay upon him, he shall pay with a valuation. But if it be perfectly formed he shall give life for life.
The Greek translators of the Bible translated "ason" as "exeikonismenon" which literally translates as "from the image," invoking the notion of "betzelem elohim"--human beings were created in God's image. The translator may have translated in this way due to the similarity between the Hebrew "ason" and the Greek "soma" meaning human life. Thinking the word meant "human life" the translator shifted it to a more theologically evocative word.
Aristotle, The History of Animals, Book VII, Part 6
In the case of male children the first movement usually occurs on the right-hand side of the womb and about the fortieth day, but if the child be a female then on the left-hand side and about the ninetieth day. However, we must by no means assume this to be an accurate statement of fact, for there are many exceptions...
About this period the embryo begins to resolve into distinct parts, it having hitherto consisted of a flesh-like substance without distinction of parts.
Philo, The Special Laws 111.108-109
But if anyone has a contest with a woman who is pregnant, and strike her a blow on the belly, and she miscarry, if the child was conceived within her is still unfashioned and unformed, he shall be punished by a fine.... But if the child which was conceived had assumed a distinct shape in all its parts, having received all its proper connective and distinctive qualities, he shall die; for such a creature as that is a man, whom he has slain while still in the workshop of nature, who had not thought it as yet a proper time to produce him to the light, but had kept him like a statue lying in a sculptor’s workshop, requiring nothing more than to be released and set out into the world.
Philo, On the Virtues
137) But the law banishes to a distance from the sacred precincts all animals which are pregnant, not permitting them to be sacrificed until they have brought forth, looking on the animals which are still in the womb as equal to what has just been born... for it is the most impious of all customs, to slay both offspring and mother at one time and on one day. (139) And it appears to me that some lawgivers, having started from this point, have also promulgated the law about condemned women, which commands that pregnant women, if they have committed any offence worthy of death, shall nevertheless not be executed until they have brought forth, in order that the creature in their womb may not be slain with them when they are put to death.
Temple Scroll 52
And you shall not slaughter a cow or a ewe and its young on the same day, and you shall not kill a mother with its young.
Sifre Zuta to Numbers 35:22
I might have thought that if she were pregnant they would postpone [the execution] until she gave birth. Therefore, the Torah teaches, “He that smote him shall surely be put to death.” I might have thought that if she were three months pregnant, they should not postpone [the execution] until she gives birth; but if she were nine months pregnant, they should postpone [the execution] until she has given birth. Therefore, Scripture teaches, “He shall surely be put to death.”
Josephus Contra Apion ii.202
The law enjoins us to bring up all our offspring, and forbids women to cause abortion of what is begotten, or to destroy it afterward. If any woman appears to have done so, she will be a murderer of her child, by destroying a living creature and diminishing human kind.
The Didache 2:1-2
Now the second command of the teaching: Thou shalt not kill…Thou shalt not murder the child in the mother’s womb nor kill the newly born.
Tertullian, On the Soul
Consider the wombs of the most sainted women instinct with the life within them, and their babes which not only breathed therein, but were even endowed with prophetic intuition. See how the bowels of Rebecca are disquieted, Genesis 25:22-23 though her child-bearing is as yet remote, and there is no impulse of (vital) air. Behold, a twin offspring chafes within the mother's womb, although she has no sign as yet of the twofold nation....
Accordingly you read the word of God which was spoken to Jeremiah, Before I formed you in the belly, I knew you. Jeremiah 1:5 Since God forms us in the womb, He also breathes upon us, as He also did at the first creation, when the Lord God formed man, and breathed into him the breath of life. Genesis 2:7 Nor could God have known man in the womb, except in his entire nature: And before you came forth out of the womb, I sanctified you. Well, was it then a dead body at that early stage? Certainly not. For God is not the God of the dead, but of the living.
Basil, 4th Century Bishop, Cappadocia, Letter 188
II. The woman who purposely destroys her unborn child is guilty of murder. With us there is no nice enquiry as to its being formed or unformed. In this case it is not only the being about to be born who is vindicated, but the woman in her attack upon herself; because in most cases women who make such attempts die. The destruction of the embryo is an additional crime, a second murder, at all events if we regard it as done with intent. The punishment, however, of these women should not be for life, but for the term of ten years. And let their treatment depend not on mere lapse of time, but on the character of their repentance.