Which, of course, includes a very large percentage (perhaps a majority) whose "contraceptive failure" involves them forgetting to take their pill, reusing a condom, using petroleum jelly as a lubricant with a condom etc. etc.
50% of dead babies killed by abortion therefore by your thought standards had "reponsible" parents.
Nope. Try again. I'll be conservative with numbers- let's say that half of all "contraceptive failure" abortions really are caused by contraceptive failure rather than improper use or irresponsibility. That means that 75% of abortions are caused by irresponsibility.
Nonetheless, those children are still needlessly dead while their parents are most likely alive. I wouldn't consider that responsible.
I'd give my life for my family, not the other way around.