Some factors affecting the secondary sex ratio in a Latin American sample.

A sample based on hospital birth records from the Latin American Collaborative Study on Congenital Malformations (ECLAMC) was used in this study. ECLAMC, which covers 11 countries (Uruguay, Chile, Argentina, Brazil, Bolivia, Peru, Paraguay, Ecuador, Venezuela, Colombia, and Costa Rica), registered 1,037,272 live births in the period 1982-1986. We applied several multivariate analysis models to the data and found that the sex ratio was significantly affected by secular, spatial (countries), biological (maternal age, birth order, and ethnic group), and socioeconomic (evaluated by hospital payment) variables. The black ethnic component carried sufficient weight to remove the spatial effect (Brazil and Venezuela) in certain cases. The Amerindian admixture effect on the sex ratio was negative and significant.