Thursday, August 5, 2010

How Long Are Pregnancies?

At the marlin party the other night, our server was pregnant.  We all know her, as she originally moved to Zamami to work for the marlin captain, then met her future husband on Zamami.

I asked when she was due and she said was six months into the pregnancy, so she had four to go.  I said, "Wait!  Six plus four is ten!  But babies only take nine months!"  The seven people there all jumped in and told me, in an 'everybody knows this' tone, that babies take ten months and ten days.

This is clearly not something I'm an expert on, but I really thought that babies took nine months.  I realize that some months have fewer days, but that doesn't account for the 40 day difference. I didn't really know what to say so I ended it jokingly saying that American babies only take nine months.

I know I could Google this, but I thought it'd be more fun to throw it on the blog.  How long do babies take?

Edit: Thanks to Julie in the comments for pointing out this very timely other blog post on the issue.  It appears that Japanese count their pregnancy months based on the lunar calendar, which makes each month a 4-week month.  Pregnancies are 40 weeks, so divide that by 4-week months and you get ten months!  (The problem, of course, is that last night when the girl was calculating her due date she was using calendar months.  Also, I wonder where the extra 10 days are coming from?  Anyway, thanks Julie!)


Cliff said...

I googled it for you. The correct answer is...

40 weeks!

Cliff said...

Maybe they are also counting the 'getting pregnant' month?

ReBekha said...

Weird! I've never head anyone say anything other than 9 months! I asked our Chinese authority (An Yang) and she said that most people in asia say 10 months but it is actually 9 ("just google it!"), then one of the Japanese teachers chimed in and said, "No! It's definitely 10 months and 10 days!" Then they fought about it. Ha ha!

Cliff said...

Just asked my female teachers. They all said 10 months and 10 days.

One of my teachers said it is 40 weeks and that in Japan, they say that one month has 4 weeks.

So that's probably where the 10 months came from.

She then busted out the calculator and did the math which came out to 9.333 months. Everyone was like, 'Huh.', then went back to work.

Julie Furber said...

Good timing I guess :)

Dave said...

Julie, perfect timing! I've added an update to the post to include your reference. Thanks!

Anonymous said...


I want to have your baby!!!

Dave said...

I'll put you on the waiting list.

bithonista said...


I know I am a bit late on this one, but I think the extra 10 days is because they count from the beginning of the lunar month. Women used (perhaps many still do) to have fertility cycles linked to the lunar cycle and they would be most fertile around the 10th day of the lunar cycle, ie - this is the time they are most likely to conceive. So forty weeks from the 10th day of the lunar cycle = 10 lunar months and 10 days from the beginning of the lunar cycle they fell pregnant...

I randomly came across your blog - think it is great. I love the look of Palau.



Anonymous said...


There is a Japanese pharase 快楽十秒 ガキ十月十日(kairaku jyubyo gaki totsuki touka).

Sir, how do you say this Japanese phrase in English?

Thank you for your help.


Dave said...

Peter, thanks for your explanation on the lunar cycle. It is amazing to be able to make sense of something that otherwise seems so random.

Anonymous, your saying is quite amusing. I think the best translation would be "10 seconds of joy equals a child in 10 months and 10 days"

Anonymous said...

Woww, these are cool comments!!!!
I LOVE them.