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Abstract
This dissertation is composed of three analyses examining the presence of seasonal and racial heterogeneity in human reproductive outcomes. The initial analysis represents the first multivariate examination of the extreme seasonality of births in Matlab, Bangladesh. A discrete-time hazards analysis is used to model the simultaneous effects of seasonal variation in labor-related migration, temperature, breast feeding cessation, and nutrition upon the monthly probability of conception. Seasonality in conceptions--and therefore births--is found to result from the synergistic effect of each of these influences upon the population fecundity level.
The second analysis examines differences in the etiology of interuterine growth retarded and premature births for black and white residents of Philadelphia. A series of logistic regressions with race-interactive terms model the odds of the occurrence of either of these adverse birth outcomes. It is shown that the racial gap in the prevalence of intrauterine growth retarded and premature births stems both from race-specific differences in the effects and from levels of a set of demographic, behavioral, and medical risk factors. The final analysis goes into greater depth in examining the racial differences in gestational duration. Ordinary least squares and quantile regressions are used to show a three to four day shorter average gestational duration among blacks net of a set of social and medical controls. Additional ordinary least squares regressions are used to demonstrate higher mean birth weights and APGAR scores at younger gestational ages among black neonates. The hypothesis is proposed that this apparent increase in black neonatal fitness earlier in gestation may be the result of an evolutionary adaptation to chronic, endemic African malaria.
