My bad

I'm studying/reading/typing up OBGYN reports in school right now. I'm also learning the mother load of abbreviations for all these reports...
I was to expand the abbreviations, and my 'corrected' page came back with this:

BPD = ?
Your Answer: bipartisian diameter
Correct Answer: biparietal diameter


I guess that's what I get for thinking about political things while taking an OBGYN test.