The best way to ensure the well-being of the child is not to even risk it. Abstinence absolutely ensures that.
Too often it fails (even in just the fact of giving into lust - then "ah, the heck with worrying about condoms"). And a child is born in poverty and ends up in the middle of some ridiculous civil suit on Judge Judy.
Or, they are aborted.
As for calling it "sin", if it were translated into science it would still prove a better thing for any child of the participant than pre-marital (and all extra-marital) sex.
I don't argue with your point. I only ask how realistic it is, given the society we inhabit and the urges that are hard-wired into us. If someone is able to maintain their abstinence, bravo for them (and I don't mean that sarcastically). But I would argue that for the vast, vast majority of the population, particularly between 18-25, there's just no way, and therefore it's best that they be well-educated as to how to best protect themselves.