No there isn't. For many years Pro Lifers were not sure exactly where they should determine that life begins. The decision that once the egg is fertilized, life is begun, served as a stake in the ground that Pro Lifers could rally around. But it's not in the Bible, it's not a technical fact. In fact it was a POLITICAL decision, not one based on faith. It allowed the GOP to co-opt the US fundamentalist/evangelical Christian movement and warp it to their own political purposes.
Just for a moment, consider an alternative. Suppose they had decided that life begins when brain waves begin. Before that, you have no consciousness, no fear or pain, no personality. When someone's brain waves cease, we call that -death-. Nobody has ever come back from brain death! So why not consider the other end of brain activity as the beginning of life?
This happens around 10 weeks, so setting this as the standard would allow a woman 6-8 weeks to learn she's pregnant (because it takes that long), then another week or two to talk to her husband, her pastor, her doctor, and make a decision. First trimester abortion, cheap, quick, safe. After that you'd need a good decision.
How reasonable! But the whole point of the Republican Pro Life thing is NOT to be reasonable. No temporary compromises that might greatly reduce abortion (and its danger) while we try to change peoples' minds. They deliberately DESIGNED this issue to be insoluble, so they could get the maximum political mileage out of it. 40 years now.