Is 40 weeks 10 months?

So, I am having a problem understanding this whole pregnancy thing being 40 weeks. Isn't 40 weeks actually 10 months, not 9 months? Was my high school health teacher completely wrong? At 21 weeks...yes, I have been thinking about this for a long time, I have had an epiphany. For those of you who don't want to calculate the Lunar cycle and how old the egg is verses how far along you are in your pregnancy, behold, I have a new way to understanding the 40 weeks. Are you ready? Here it is:



52 weeks in the year minus 40 weeks = 12 weeks.

12 weeks = 3 months, therefore, 40 weeks = 9 months



This is the best I can come up with.