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A sample based on hospital births recorded for the Latin American Collaborative Study on Congenital Malformations (ECLAMC) program was used in the present study to determine sex ratios for live births and for stillbirths. Sixty-four cities and 147 hospitals in 11 countries (Uruguay, Chile, Argentina, Brazil, Bolivia, Peru, Paraguay, Ecuador, Venezuela, Colombia, and Costa Rica) were included in the present analyses. The number of live births was 1,886,653 in the period 1967-1986, and the number of stillbirths was 24,818 in the period 1978-1986. The sex ratio for the total sample was 0.5112 for live births and 0.5477 for stillbirths. The sex ratio as a whole is decreasing with time in a parabolic fashion. Each country in our study behaved differently. Except for Peru and Uruguay. the countries experienced a significant decrease in the sex ratio after 1978 for live births: only Brazil did not show a temporal trend for the sex ratio for stillbirths. [ABSTRACT FROM AUTHOR]

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.