That’s the technical, scientific explanation for when a new human life begins. There is no debate over this.
Things get stickier when you actually need to decide when life begins to matter. When does killing a growing human change to murder? Or is it always murder? Does the morality change at all?
When does the zygote/embryo/fetus actually become a person? Opinions I have heard follow:
1. When the first brain waves are recorded. (There is debate over this. There’s debate over virtually every aspect about the timing of development of the fetus.)
2. When the heart begins to beat. (Obviously a functioning body now.)
3. When the fetus can feel pain. (Again, a lot of debate, and, if I may say so, a lot of lies.)
6. When the baby breathes. (I do not get this one. How does this mean personhood?)
7. When the umbilical cord is cut. (I don’t get this one either.)