There are plenty of other ways to keep population under control that do not make life trivial. All kinds of birth control and contraceptives are available and affordable. And I'd wager to say that a vast majority of unwanted births do not result from malfunctions of these products. Plus there are plenty of people who would like to adopt, just too much red tape in their way.
America and Europe have stable or declining populations and abortions are not a major part in that.
For one thing, the people who have the most accidental children tend to be in demographic groups that are opposed to abortion. And the people who don't overpopulate have a tendency to be more responsible and avoid having children.
I don't think abortion should be accepted unless it's a case in which the mother's health is in danger or the baby is overwhelmingly likely to be stillborn or born with a mortal or brain-damaged condition.

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"Man lives in the sunlit world of that which he believes to be reality. But unseen by most is an underworld, a place that is just as real... but not as brightly lit... A DARK SIDE!"
-opening from Tales From the Darkside