Japanese journal of human genetics

, Volume 25, Issue 2, pp 73–81 | Cite as

Analysis of multiple birth rates in Japan

III. Secular trend, maternal age effect and geographical variation in triplet rates
  • Yoko Imaizumi
  • Eiji Inouye


Over-all triplet birth rate in Japan was decreased during 1955 to 1967 and 1974. Monozygotic rate was slightly decreased with the year, but dizygotic rate as estimated from monozygotic and dizygotic twinning rates was decreased with the year. Trizygotic rate was increased with the year and particularly high in 1974.

Monozygotic rate was slightly increased up to the maternal age group of 35–39 years and decreased thereafter. Similar but more marked pattern is seen for dizygotic rate, whereas trizygotic rate seems to be independent of maternal age. Analysis of secular change during the period from 1960 to 1967 indicated a clear decrease of monozygotic rate in the older maternal age groups. The maternal age effect on the increase of trizygotic rate is less clear.

The highest monozygotic rate was seen in the northeast Hokkaido District (56 per million). On the other hand, dizygotic rate was slightly higher in the northeast than in the southwest. As to trizygotic rate, the highest rate was seen in the southwest Kyushu District (10 per million). Heterogeneity of geographical variation was indicated in monozygotic and trizygotic rates, but not in dizygotic rate.

Underrepresentation of unlike-sexed triplet sets was suggested in two districts. After excluding the two districts, corrected monozygotic rate is 30, and dizygotic and trizygotic rates are 18 and 7 per million, respectively.


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  1. Allen, G. 1960. A differential method for estimation of type frequencies in triplets and quadruplets.Am. J. Hum. Genet. 12: 210–224.PubMedPubMedCentralGoogle Scholar
  2. Allen, G., and Firschein, I.L. 1957. The mathematical relations among plural births.Am. J. Hum. Genet. 9: 181–190.PubMedPubMedCentralGoogle Scholar
  3. Brackenridge, C.J. 1978. Aspects of the increasing triplet rate in Australia.J. Biosoc. Sci. 10: 183–188.CrossRefPubMedGoogle Scholar
  4. Bulmer, M.G. 1970.The Biology of Twinning in Man. Clarendon press, Oxford.Google Scholar
  5. Imaizumi, Y., and Inouye, E. 1979. Analysis of multiple birth rates in Japan. I. Secular trend, maternal age effect, and geographical variation in twinning rates.acta Genet. Med. Gemellol. 28: 107–124.CrossRefPubMedGoogle Scholar
  6. Inouye, E. 1957. Frequency of multiple birth in three cities of Japan.Am. J. Hum. Genet. 9: 317–320.PubMedPubMedCentralGoogle Scholar
  7. Japan, Ministry of Health and Welfare. Annual, 1951–1968 and 1974. Vital Statistics, Health and Welfare Statistics and Information Department, Ministry of Health and Welfare, Tokyo.Google Scholar
  8. Japan, Ministry of Health and Welfare. 1977. Survey on Socio-Economic Aspects of Vital Events-Plural Births, 1975. Health and Welfare Statistics and Information Department, Ministry of Health and Welfare, Tokyo.Google Scholar
  9. Jeanneret, O., and MacMahon, B. 1962. Secular changes in rates of multiple births in the United States.Am. J. Hum. Genet. 14: 410–425.PubMedPubMedCentralGoogle Scholar
  10. Komai, T., and Fukuoka, G. 1936. Frequency of multiple births among the Japanese and related peoples.Am. J. Phys. Anthropol. 21: 433–447.CrossRefGoogle Scholar
  11. Milham, S., Jr. 1964. Pituitary gonadotropin and dizygotic twinning.Lancet 2: 556.Google Scholar
  12. Nylander, P.P.S. 1973. Serum levels of gonadotrophins in relation to multiple pregnancy in Nigeria.J. Obst. Gynaecol. Br. Commonw. 80: 651–653.CrossRefGoogle Scholar
  13. Rola-Janicki, A. 1974. Multiple births in Poland in 1949–1974.Acta Genet. Med. Gemellol. 22: Supple.: 202–209.PubMedGoogle Scholar
  14. Sawazaki, C., and Tsubata, H. 1976. Statistics of multiple births in Japan.Sanka to Fujinka 43: 863–869 (in Japanese).Google Scholar
  15. Soma, H., Takayama, M., Kiyokawa, T., Akaeda, T., and Tokoro, K. 1975. Serum gonadotropin levels in Japanese women.Obst. and Gynecol. 46: 311–312.Google Scholar

Copyright information

© Business Center for Academic Societies 1980

Authors and Affiliations

  • Yoko Imaizumi
    • 1
  • Eiji Inouye
    • 2
  1. 1.Institute of Population ProblemsMinistry of Health and WelfareTokyoJapan
  2. 2.Institute of Brain ResearchUniversity of Tokyo School of MedicineTokyoJapan

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