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Zygosity Misclassification of Twins at Birth in Japan

Published online by Cambridge University Press:  21 February 2012

Syuichi Ooki ,
Yoshie Yokoyama  and
Akio Asaka
Syuichi Ooki*
Affiliation:
Department of Health Science, Ishikawa Prefectural Nursing University,Tsu7-1 Nakanuma,Takamatsu, Kahoku, Ishikawa, Japansooki@kj8.so-net.ne.jp
Yoshie Yokoyama
Affiliation:
Department of Health Science, School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan
Akio Asaka
Affiliation:
Joto Hospital, Joto Kofu,Yamanashi, Japan
*
*Address for correspondence: Syuichi Ooki, Department of Health Science, Ishikawa Prefectural Nursing University, Tsu7-1 Nakanuma, Takamatsu, Kahoku, Ishikawa, 929-1212, Japan.

Abstract

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Though twinning rates have been rapidly increasing in Japan, the problem of zygosity misclassification at birth has been paid little attention. By analyzing four independent samples, the authors found that at a constant rate about 25–30% of monozygotic twins were misclassified as dizygotic twins at birth. This percentage is in very good accordance with that of monozygotic twins having dizygous placenta. Generally the obstetricians informed twins' parents about their children's zygosity. The number of placentas, as informed by obstetricians, was very strongly associated with zygosity. Concluding, even now many monozygotic twins in Japan may be misclassified as dizygotic at birth by obstetricians based solely on the number of placenta.

Type
Articles
Information
Twin Research and Human Genetics , Volume 7 , Issue 3 , 01 June 2004 , pp. 228 - 232
Copyright
Copyright © Cambridge University Press 2004