[Relationship between reproductive patterns and infant mortality: alternative interpretations]

A secondary analysis of the data of the Mexican National Fertility and Health Survey of 1987 (ENFES for its spanish acronym) was undertaken in order to study the relationship between reproductive patterns and child mortality. A total of 13,216 births and 711 infant deaths occurred 1 to 15 years previous to the survey were studied. The main conclusions are: 1) it is the adverse social, economic and environmental conditions surrounding young mothers (15 to 19 years) which are responsible for the excess mortality found in their children; 2) children of older women (35 and more years) experience increased mortality only in the late fetal period, this suggesting that a biological mechanism is mainly at stake; 3) the relative risks of death of first births, as compared to subsequent ones are generally smaller than one, indicating that first births have a lower probability of dying. The relative risk of death of first born relative to subsequent births, on the other hand, decreases with increasing age at death, suggesting that biological factors such as low birthweight and intrapartum complications are possibly important as well; 4) relative risks of death for short-spaced as compared to well spaced births were found, in general, to decrease from the late fetal to the neonatal and to the postneonatal periods. This points to a biological pathway, possibly via maternal nutrition, for the effect of spacing on child mortality.