Did you know Japanese women are pregnant for 10 months?
But, it's probably not how your thinking. Every woman is the world, Japan included, is pregnant for about 40 weeks. The difference is how the western world and Japan count those months.
In the States, pregnancy is counted by calendar months. Every month, is between 4 and 5 weeks long (with the exception of February, which just likes to be different).
In Japan, pregnancy is broken up into 10 4-week "months."
It took me some time to wrap my head around it, so I made this handy chart.
Both systems have their up-sides: counting with calendar months makes estimating a due date much easier. Also, trimesters are broken up more easily into 3 3-month periods.
With the Japanese way, I always know what months I'm in with out having to consult "What to Expect When You're Expecting."
I am 4 months pregnant in the US and 5 months pregnant in Japan.
Luckily for us, both countries also count pregnancies by weeks. To make things easier, I tend to default to weeks when ever someone asks how far along I am.