Monica Hesse: Ignorance about the female body hurts us all

I was trying to schedule a sonogram last year when my understanding of a basic scientific principle was totally upended. The nurse, attempting to discern how pregnant I might be, turned out to be utterly uninterested in the date of conception. She only wanted to know the date of my last period. That, she explained, is how pregnancy is calculated. Which meant that as far as the medical community was concerned, I was technically five weeks along, even though there was no way I could physically be more than three. Those two previous weeks, I guess I was .