Let's look at the facts. One estimate is that even without birth control about 80% of fertilized eggs never reach the end of the first month. They either never attach to the uterine wall or disconnect for any one of a variety of reasons. Discounting stillbirths and crib death, we're talking about 24 BILLION dead zygotes just for the 6 billion people alive today.
Now, since we are all tainted with original sin, this means if those zygotes have souls they go straight to Hell when they're passed by the woman's body.
This means our loving God who came to Earth and died for our sins has no problem with 24 Billion souls going straight to Hell without even having drawn their first breath or even had their first heartbeat. If you want to argue that life begins at fertilization then you're also stuck with a cold, heartless God who damns 80% of all humans right off the bat. Unless you're Catholic, and the Pope declares Limbo valid this month. In that case there's 24 Billion souls in limbo instead of Hell.
And that's just for the people alive today That ignores all the generations that came and went before us.