And yet we strive to prevent heart attacks, despite their natural nature.
We strive to prevent heart attacks but we don't consider them a crime. Saying that a lot of natural "abortions" happen therefore it is ok to cause a few more is the same thing as saying a lot people die in accidents so its ok to kill a few more.
Logically the religious view is consistent here, and this argument is as silly as the one often made about the alleged hypocrisy of religious people caring fanatically about fetus right to life and yet supporting the death penalty - not inconsistent where you realize that "right to life" is a shorthand for right to life of innocent people, in this case the unborn ones, not an absolute in all cases.
I think the correct argument for abortion is the libertarian one of absolute property right over one's own body. Fetus may have the right to life or not, but it does not have the right to use another person's body in order to survive without that person's consent.