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Multiple Birth Rates in Japan: Further Analysis

Published online by Cambridge University Press:  01 August 2014

Y. Imaizumi*
Affiliation:
Institute of Population Problems, Ministry of Health and Welfare, Tokyo, Japan
E. Inouye
Affiliation:
Institute for Developmental Research, Aichi Prefectural Colony, Aichi, Japan
*
Institute of Population Problems, Ministry of Health and Welfare, 1-2-2 Kasumigaseki, Chiyoda-Ku, Tokyo 100, Japan

Abstract

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The rates of MZ and DZ twin births and of triplet births slightly decreased in Japan in 1955-1967 and 1974, whereas that of trizygotic triplets tripled. The rates of triplet and quadruplet births were comparable to those of Caucasians. Although the sample size is small, Japan seems to be characterized by higher rates of triplets and quadruplets of polyembryonal origin and lower rates of those of polyovulational origin as compared to Caucasian populations. Stillbirth rates in both MZ and DZ twins gradually decreased in 1960-1967 and 1974. The rate was higher in MZ than DZ twins, and higher in males than females. The secular trends of stillbirth rates in like-sexed triplets was similar to that in twins, whereas the rate in unlike-sexed triplets remained almost constant for the entire period. The rate was higher in like-sexed than unlike-sexed triplets.

Type
Research Article
Copyright
Copyright © The International Society for Twin Studies 1984

References

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