@Rarebear The Bible does not say that life begins at conception, and in fact says quite differently. One of the most commonly cited passages from the anti-abortion crowd is from Psalm 139. This is the passage that @KNOWITALL cited, but it is no coincidence that the website from which she got the passage omits verses 14 and 16. The full section runs as follows:
”[13] For you created my inmost being; you knit me together in my mother’s womb. [14] I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well. [15] My frame was not hidden from you when I was made in the secret place, when I was woven together in the depths of the earth. [16] Your eyes saw my unformed body; all the days ordained for me were written in your book before one of them came to be.”
In Hebrew, this is:
13 כִּֽי־אַ֭תָּה קָנִ֣יתָ כִלְיֹתָ֑י תְּ֝סֻכֵּ֗נִי בְּבֶ֣טֶן אִמִּֽי׃
14 אֹֽודְךָ֗ עַ֤ל כִּ֥י נֹורָאֹ֗ות נִ֫פְלֵ֥יתִי נִפְלָאִ֥ים מַעֲשֶׂ֑יךָ וְ֝נַפְשִׁ֗י יֹדַ֥עַת מְאֹֽד׃
15 לֹא־נִכְחַ֥ד עָצְמִ֗י מִ֫מֶּ֥ךָּ אֲשֶׁר־עֻשֵּׂ֥יתִי בַסֵּ֑תֶר רֻ֝קַּ֗מְתִּי בְּֽתַחְתִּיֹּ֥ות אָֽרֶץ׃
16 גָּלְמִ֤י ׀ רָ֘א֤וּ עֵינֶ֗יךָ וְעַֽל־סִפְרְךָ֮ כֻּלָּ֪ם יִכָּ֫תֵ֥בוּ יָמִ֥ים יֻצָּ֑רוּ אֶחָ֣ד בָּהֶֽם׃
The talk of being woven together in the depths of the earth is directly parallel to a belief found in the ancient Greek mystery religions, which were historically quite influential on Judaism. According to these religions, human bodies were of subterranean origin and magically transported to the womb (which people back then believed was only a fertile resting place and not somewhere that a body could develop, thus why the various homuncular theories of human development originated at the same time).
This is just one of the many elements Judaism (and later, Christianity) borrowed from the Greek religions (especially pre-Olympian Greek religions). The doctrine is related to the ancient Greek view that we exist before conception even happens in the form of our soul, and that we must wait for our body to be fully formed so that we can then be attached to it. Plato used the idea to support his theories of knowledge and reincarnation. And as @Aster notes, some Christians still believe this (e.g., Mormons).
We can get out of this uncomfortable association by saying that the passage is metaphorical, but then we can no longer use it to support the notion that life begins at conception. Of course, we can’t use it that way in the first place since—as @rojo has already noted—the passage says nothing about conception and speaks only of God’s foreknowledge. The same holds true of the other passage that was cited to you, for Jeremiah 1:5 says that God knows about us before we are even conceived. Again, it is a passage about God’s foreknowledge. It tells us that God’s omniscience is not limited to the past and the present, but extends into the future as well.
This only speaks against the passages on offer, but there are other passages that speak against the thesis they were offered to support. The words most commonly used to refer to the human soul or spirit, are נשמה (neshama = “breath”) and רוח (ruach = “wind,” or “breath” by analogy). For reference, the term “holy spirit” comes from רוח הקודש (ruach hakodesh). This equivalence of “soul” and “breath” can be found in many passages, such as Genesis 2:7, Genesis 7:15, Deuteronomy 20:16, Ecclesiastes 12:7, Isaiah 42:5, Job 33:4, Ezekiel 37:5–6, Joshua 11:11, 1 Kings 15:29, John 3:5–8, and John 20:22.
Again, there is a parallel to the Greek usage of πνευμα (pneuma = “wind” or “breath,” with a connotation of being in motion as in blowing). The other Greek word that means “soul,” ψυχη (psuche or psyche), also comes from the verb “to blow” (and eventually comes to mean “mind,” which is where we get “psyche” and “psychology”). Indeed, we see this and the chthonic elements of early Greek thought come together in Genesis 2:7 when God makes Adam’s body out of earth and then makes him into a living thing by breathing into him. This is probably why modern Judaism holds that people do not come to have a soul until their first breath (though my understanding is that Jewish law grants the right to life upon one’s head exiting the mother’s body during childbirth).
Finally, there are several passages in the Bible that suggest a fetus is not of any intrinsic value. Exodus 21:22 tells us that the penalty for causing a miscarriage is a fine, whereas Exodus 21:23 tells us that the penalty for ending a life is to be killed oneself. It therefore follows that miscarriage must not, according to the law given in Exodus, count as ending a life. This is in keeping with Genesis 38:24, in which being pregnant does not prevent Tamar from being sentenced to immediate death by immolation. It also accords with Leviticus 27:1–7, in which we find out the monetary value of people by age and sex. No one below one month of age is given any value at all (just as how, in Numbers 3:15, only males a month old or more are considered persons to be counted by the census).
The clearest case, however, might be found in Numbers 5:11–31. There we learn that any man who has the merest suspicion that his wife might have been unfaithful may be brought to a priest for a test. If she is guilty, this test will abort whatever pregnancy might be in progress and sterilize her for life. If she is innocent, then she will not be harmed. Note that there is no consideration whatsoever to the possible fetus. All that matters in this scenario is that no man be forced to raise a child that he did not sire. Like the case of Tamar, pregnancy is not considered an extenuating circumstance.
No doubt, someone will find themselves with an irresistible urge to post passages that seem to contradict the ones I have cited above. All this will prove, however, is that the Bible is internally inconsistent. The problem with internal inconsistency is that it engenders self-contradiction. Statements that are self-contradictory are necessarily false, and sources that contain them are always suspect. Highlighting inconsistencies in the Bible, then, cannot help any argument that seeks to establish its legitimacy by appealing to Scripture.
(And to think that some people say studying classics and ancient philosophy has no practical uses…)