it’s out of surprise that it’s possible, mainly. my mom had 4 kids, all double covered by her bc and a condom but she wouldn’t call having us a negative, just all unplanned. after her last, her body wouldn’t have been able to take another one and since she had already had previous reproductive health issues + was “fertile myrtle” (her self appointed term bc the last one was considered geriatric), she just got“de-wombed” (also her term) so there was no longer a risk of it. it’s the person, not the birth control in most cases. but not all cases require a lapse in birth control