I found it interesting that in Matthew 1:20, after Mary is found to be with child, Joseph is told by the Angel of the Lord that "the child who has been conceived in her is of the Holy Spirit." Notice that the focus in Scripture at this point moves from the pregnant state of Mary back to the event of conception.
Looking up the Greek on this I was also struck by the fact that what is translated as "conceived" here is a word that is usually translated as "fathered". It seems to read: "the fathering was of the Holy Spirit."
Furthermore, sometimes this word is used in reference to birthing. More and more it seems the whole "conception" process as seen in the words of Scripture is all-inclusive, from the coming together of man and wife to the very birth of the child.
“Joseph, son of David, do not fear to take Mary as your wife, for that which has been conceived in her is from the Holy Spirit.
The word translated here as "has been conceived in her" is γεννηθὲν, from the verb γεννάω (gennaó): to beget, to bring forth.
Word Origin: from genna (descent, birth)As you can see, this same word is used for multiple stages and aspects of procreation, lending a greater sense of the whole than modern language and thought.
Definition: to beget, to bring forth
NASB Word Usage
bear (1), bearing children (1), became the father of (4), became...father (1), begotten (4), bore (1), born (41), Child (1), conceived (1), father (37), Father (1), gave (1), gives birth (1), produce (1).
In contrast, we moderns want to split procreation up into definable steps, each with its own special word and level importance or inviolability. For example, we have gamete formation and the various steps of copulation, fertilization and implantation. Then we have at one point a zygote then an embryo and finally a fetus. And of course we have three trimesters and finally the process of birth.
Furthermore, each of these can be further divided up into other steps and processes, each with its own name. The result is that we lose the mysterious totality of God's fearful and wonderful act of creating a human being.
Is a person formed at fertilization? implantation? the first trimester? the second? at birth? Yes, yes, yes, yes, and yes! God creative hand is at work, forming a human being throughout the whole process, from gamete formation, the love of husband and wife, the process of fertilization and all the way through the miraculous process of birth.
As we read in Hebrews 7, "One might even say that Levi himself, who receives tithes, paid tithes through Abraham, for he was still in the loins of his ancestor when Melchizedek met him." And, as the Psalmist sings: "For you formed my inward parts; you knitted me together in my mother’s womb. I praise you, for I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well."
And, as a commenter pointed out below, The ESV renders Ecclesiastes 11:5, "As you do not know the way the spirit comes to the bones in the womb of a woman with child, so you do not know the work of God who makes everything." We cannot claim to know that which God says we cannot know. Even common sense itself tells us that we cannot observe or define the moment of a supernatural act. Scripture does not specify the exact moment in the biological process at which the supernatural process of ensoulment occurs.
So, why do Satan, the world, and our sinful nature want to split the whole of procreation up into little definable stages and states of being? Why? So greater or lesser degrees of respect for the inviolability of each step can tempt us into believing we have the "right" to interfere with the miracle of procreation at this or that point. Some people think they have a right to end the process at any point up until the baby's head exits the womb. Some people think the end of the first trimester ought to signal the final opportunity to exert a woman's "choice". Some people think life begins at implantation, and others think fertilization. Some people even think they have the right to decide to only have sexual relations with their spouse when procreation is virtually impossible.
In contrast, the Bible talks about the process of procreation as a unified whole, from the loins of the father to the womb of the mother all the way through birth. Anything that interferes with God's procreative purpose at ANY point is seen as sinful in Scripture.