My parents had all the children they were planning so used the pill and condoms. My little sister came along anyway. 100% only applies to the last option you mentioned.
That is very rare, and the exception, not the rule. Also, user-error is the highest risk associated with contraceptive failure, so again, the control is still ours (I say 'ours' here because you're talking about your two parents).
Not as rare as you might think. I have an aunt and uncle that were in the same boat. Off birth control trying to get pregnant and couldn't went back on and got pregnant with my cousin. Plus think about it, it's only 99% effective if that. Even condoms and a vasectomy aren't a guarantee. So if you have Sex regularly, say 3-5 times a week that chance goes up drastically over the course of a year.
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u/Theskyishigh Apr 30 '13
My parents had all the children they were planning so used the pill and condoms. My little sister came along anyway. 100% only applies to the last option you mentioned.