I think it's generally conceded by people who think about things like this, that nature is careful of the species, but careless of the individual.
This of course flies in the face of the liberal point of view that everyone is important, or, as our President likes to say, "Everyone is entitled to a fair shot."
It's a complicated issue and made even more complex by the dichotomy presented by our religious/right and atheistic/left factions.
The religious adopt what could seem to be the egalitarian point of view: Every human being, including zygotes, should be equal and enjoy life - at least until they die a natural, if painful, death, or require execution.
They don't care how they live...sick, poor or starving....just so they are not allowed to slip the surly bonds of earth before appropriate suffering.
Whereas we atheists are generally in favor of allowing the old and ill to check out early, and permit the elimination of any inconvenient or unhealthy zygotes that pop up in our wombs.
But we want to feed and offer succor to the world.
It's a puzzle, isn't it?