The best way to go about it would be - try not to get loving pregnant in the first place.
Only in justifiable situations like say, a person getting raped, or the child putting the mother's life at risk should abortion be considered.
I do not see being careless and getting pregnant, especially with all the birth control we have nowadays, as a good reason to abort. Allowing abortion for every situation just promotes carelessness
Birth controls aren't infallible. Pills are notoriously bad for failing if you aren't strict on when you take them.
Other more effective birth controls may also be impossible for certain people with allergies or conditions. Even condoms can fail and it's possible to be allergic to latex.
Pregnancies also go unmissed for some time, and girls can go a long time before symptoms appear, when it is now too late for emergency contraceptives.
It's not always down to being careless, it can just be bad luck.
Abortions are still scary, deeply unpleasant things which can even damage your fertility. It's not something most people would go into without thought (and if there was lack-a-daisy repeat customer, maybe aborting their foetuses is a good thing).
Even if abortions for everyone did promote carelessness then it's better than having many more unwanted children born.
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