I am quite certain that a lot of those who claim that human life (in the sense of life that is worthy of protection) starts with conception /fertilization do not know that about 50 to 70 per cent of fertilized eggs do not implant in the uterus.
After fertilization happens in the fallopian tube the body checks the zygote and in case there is something wrong with it, it is flushed out with the next menstrual bleeding, an early stage miscarriage not noticed by the woman.

One could say that mother nature not only selects "human beings" (and the defective ones are sorted out) but also practices a sort of early abortion, and given that - according to those who believe that human life starts with fertilization - God has created the human body the way it is, one could say that Nature or God are abortion doctors: yes, 50, maybe even 70 per cent of "human beings" are regularly and naturally "killed" before they are born (even in Saudi Arabia or Alabama).