The people who say, "You chose to have sex, so you CHOSE to get pregnant (even if you were using birth control)" are despicable. I have to imagine to myself that they're 12-year-olds with very little experience of the real world to be making that kind of statement.
I personally know a person who got pregnant on a high dose of hormonal birth control, another who got pregnant with an IUD, and a third who got pregnant at the very end of perimenopause when she thought her periods had stopped.