I Did Not Know That, OB/GYN Edition

Following a link recently, I came across a New York Times article from over a year ago about the morning-after pill. I learned you have one chance in forty of getting pregnant after unprotected sex if you use the morning-after pill, compared to one chance in twenty without. Maybe everybody knew this already,  but once I did a little math, there were a couple of implications that I found startling:

• The morning-after pill only cuts your chances of becoming pregnant in half, which is not all that reassuring. Half of the people who would have gotten pregnant will get pregnant anyway. 

• Without the morning-after pill, you would need to have unprotected sex thirteen times to have a fifty percent chance of getting pregnant.

If I were the father of a teenage girl, I'd want her to know the first but not the second.