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Changing Trends in Twinning*

Published online by Cambridge University Press:  01 August 2014

R. Goswami
Affiliation:
Department of Genetics, The University Campus, Bhopal 462026, India
H.K. Goswami*
Affiliation:
Department of Genetics, The University Campus, Bhopal 462026, India
*
Department of Genetics, Bhopal University, Bhopal, 462026, India

Abstract

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Birth statistics (on 13,887.943 births) from 11 Indian States indicate a fall in the dizygotic twinning rate and a rise in the monozygotic twinning rate over the decade between 1982 and 1991. These figures seem to reverse the trend of the period 1960-1982. One plausible explanation is offered by the age-data on mothers, which indicate that twins of different sex are more frequently born to mothers above the age of 35. Since extensive family planning measures have reduced the upper age-limit of mothers, the birth-rate of twins of different sex has also fallen. Due to the increased proportion of twins of the same sex, Weinberg's differential method will therefore report a decline in the dizygotic twinning rate, wherever the mean age of mothers has fallen (i.e. most mothers do not reproduce after the age of 35).

Type
Research Article
Copyright
Copyright © The International Society for Twin Studies 1993

Footnotes

*

This data was presented at the 7th International Congress on Twin Studies, held in Tokyo from 22-25 June, 1992.

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