This reader is right, and my catechetics obviously require refreshing:
What kind of a Catholic are you? The insurance policy was not to insure against 'immaculate conception,' but virgin birth. The doctrine of the Immaculate Conception is that the Virgin Mary was conceived in the womb of her mother free from all stain of original sin, so that she might be a spotless vessel when carrying the Christ. Her own conception, however, was by otherwise normal means between Anna and her husband Joachim.
Forgive me. I have muddled that up before. This, by the way, is how I first discovered the facts of life. I was in a religious instruction class on the "immaculate conception". It made no sense to me at first. What would a "maculate conception" be, I asked my teacher? He sighed, realized it was time for the talk and went into the basics. I was ten. I didn't believe a word of it. I found it far easier to believe that Mary was born without sin than that my parents had done that to conceive me. But I digress ...