I learned those canine facts upon seeing the “doggie diapers” as a young child. And somehow it got mixed up in my older-child mind with more recently acquired facts about human menstruation.
So I was under the impression that human females could only become pregnant while menstruating, and consequently was baffled by talk about the importance of birth control, because it seemed like it would be trivially easy to just avoid impregnation-type activities during your period.
I remain eternally grateful to the seventh-grade Health Ed teacher who cleared up that, um, misconception before it had any life-altering consequences for me.