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Modern and Traditional Japanese Culture: The Psychology of Buddhism, Power Rangers, Masked Rider, Manga, Anime and Shinto. 在日イギリス人男性による日本文化論.

Wednesday, March 22, 2006


How many months pregnant?

How many months pregnant?
Originally uploaded by timtak.
In Japan the length of pregnancy is said to be 10 months. This is because the Japanese measure pregnancy in terms of lunar months, or rather menstrual cycles, from the date of the last normal period to birth. There are ten cycles, so pregnancy is deemed as being ten months long.

Westerners on the other hand measure pregnancy in calendar months from the date of conception, which is 38 weeks, or approximately 9 calendar months.

Aparently in Western prenatal clinics too, gestation is measured from the first day of the last menstrual cycle, which is also the first day of menstruation.

What I am not clear about is what marks the beginning of gestation, or the menstrual cycle. Cycles do not have beginnings and ends, since they are circlular.

I guess that one reason is clarity - there is menstrual blood on this day and so the event can be timed and days can be counted. But that seems like an arbitary length of time for both Japanese and Western medics to deem the beginning of gestation.

Is there a medical basis, perhaps in the fact that this is the day that the mother's temperature drops, and stays low until ovulation and Western web sites say that pregnancy is medically, 40 weeks long too?

Yasuko suggested that the current system, is based upon the transmogrification of the soul: when one egg is thrown out, the soul moves to next egg, so the life of the next egg starts at the death of the previous one.

I am not sure why gestation should be deemed to start at the death of the previous egg. Or why the menstrual cycle should be said to "start" at menstruation instead of at the end of the "previous" mensturation, or at ovulation - the day that the egg leaves the ovum.

One might argue that gestation is the time that the egg is in preparation but, in a sense the egg has been in preparation since the mother was born, or even before that. One could arge that pregnancy is almost infinite!

Upon investigation, measuring gestation from the time of the "last normal period" does seem to be arbitary - based upon a time that can be measured (when conception / ovulation are often more difficult to ascertain).

I guess that is more natural to say that pregnancy is precisely 10 womens-months since when we are talking about the cycles, periods, time span of a woman's body. If one uses calendar months then there is going to be error in estimating the babies developement depending on the length of the month.

I am told that when Western prenatal clinics characterise the development of the foetus, they also use 4 week months (to avoid error caused by the lengths of gregorian months) but in order to make pregnancy fit the calendar the first and last months are considered to be 6 weeks long.

In any event, it seems that the length of pregnancy in Japan is measured in a more natural, female oriented way, from the time of mother's last mensturation in menstrual cycles. Since it is women that do pregnancy, and it is their bodies, this seems like a very sensible way of measuring things.

In the West pregnancy is measured in a more male-oriented fashion, as the number of Gergorian calendar months from the time of conception - when the guy gets involved.

The fact that some Japanese misconcieve the length of pregnancy to be ten calendar months is discussed here. As I mention on that forum, I think that Westerner's characterisation of pregnancy as being nine calendar months involves a misconception too. No pun intended.

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This blog represents the opinions of the author, Timothy Takemoto, and not the opinions of his employer.