Population-Based Study of Sex Proportion in Monoamniotic Twins
- 14 July 1988
- journal article
- Published by Massachusetts Medical Society in New England Journal of Medicine
- Vol. 319 (2) , 119-120
- https://doi.org/10.1056/nejm198807143190215
Abstract
To the Editor: In humans, the proportion of males at birth, or sex proportion, varies between 0.510 and 0.517 and is remarkably constant among different countries and over time. The overall sex proportion of twins and higher-order multiple births is slightly lower than that of single births.1 There is evidence that monozygotic twins have a lower sex proportion than dizygotics,2 but no population-based data on the sex proportion of twins with known zygosity and placentation are available.In the course of the East Flanders Prospective Twin Study, started in 1964,3 we examined the sex proportion in 2811 consecutively born pairs . . .Keywords
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